diff --git a/apps/remix/app/components/general/admin-email-blocklist-section.tsx b/apps/remix/app/components/general/admin-email-blocklist-section.tsx
new file mode 100644
index 000000000..7d074621a
--- /dev/null
+++ b/apps/remix/app/components/general/admin-email-blocklist-section.tsx
@@ -0,0 +1,171 @@
+import {
+  SITE_SETTINGS_EMAIL_BLOCKLIST_ID,
+  type TSiteSettingsEmailBlocklistSchema,
+} from '@documenso/lib/server-only/site-settings/schemas/email-blocklist';
+import { trpc as trpcReact } from '@documenso/trpc/react';
+import { Button } from '@documenso/ui/primitives/button';
+import {
+  Form,
+  FormControl,
+  FormDescription,
+  FormField,
+  FormItem,
+  FormLabel,
+  FormMessage,
+} from '@documenso/ui/primitives/form/form';
+import { Switch } from '@documenso/ui/primitives/switch';
+import { Textarea } from '@documenso/ui/primitives/textarea';
+import { useToast } from '@documenso/ui/primitives/use-toast';
+import { zodResolver } from '@hookform/resolvers/zod';
+import { msg } from '@lingui/core/macro';
+import { useLingui } from '@lingui/react';
+import { Trans } from '@lingui/react/macro';
+import { useForm } from 'react-hook-form';
+import { useRevalidator } from 'react-router';
+import { z } from 'zod';
+
+const ZEmailBlocklistFormSchema = z.object({
+  enabled: z.boolean(),
+  domains: z.string(),
+});
+
+type TEmailBlocklistFormSchema = z.infer<typeof ZEmailBlocklistFormSchema>;
+
+/**
+ * Splits a comma-separated string into a normalised list of domains.
+ * Normalisation (trim, lowercase, strip leading "@", dedupe) is applied
+ * server-side by the schema as well — this is for display consistency.
+ */
+const parseDomainsInput = (value: string): string[] => {
+  return Array.from(
+    new Set(
+      value
+        .split(',')
+        .map((entry) => entry.trim().toLowerCase().replace(/^@/, ''))
+        .filter((entry) => entry.length > 0),
+    ),
+  );
+};
+
+type AdminEmailBlocklistSectionProps = {
+  emailBlocklist: TSiteSettingsEmailBlocklistSchema | undefined;
+};
+
+export const AdminEmailBlocklistSection = ({ emailBlocklist }: AdminEmailBlocklistSectionProps) => {
+  const { toast } = useToast();
+  const { _ } = useLingui();
+  const { revalidate } = useRevalidator();
+
+  const form = useForm<TEmailBlocklistFormSchema>({
+    resolver: zodResolver(ZEmailBlocklistFormSchema),
+    defaultValues: {
+      enabled: emailBlocklist?.enabled ?? false,
+      domains: (emailBlocklist?.data?.domains ?? []).join(', '),
+    },
+  });
+
+  const enabled = form.watch('enabled');
+
+  const { mutateAsync: updateSiteSetting, isPending: isUpdateSiteSettingLoading } =
+    trpcReact.admin.updateSiteSetting.useMutation();
+
+  const onBlocklistUpdate = async ({ enabled, domains }: TEmailBlocklistFormSchema) => {
+    try {
+      const parsedDomains = parseDomainsInput(domains);
+
+      await updateSiteSetting({
+        id: SITE_SETTINGS_EMAIL_BLOCKLIST_ID,
+        enabled,
+        data: {
+          domains: parsedDomains,
+        },
+      });
+
+      // Reflect the normalised value back in the form.
+      form.reset({
+        enabled,
+        domains: parsedDomains.join(', '),
+      });
+
+      toast({
+        title: _(msg`Email Blocklist Updated`),
+        description: _(msg`The email blocklist has been updated successfully.`),
+        duration: 5000,
+      });
+
+      await revalidate();
+    } catch (err) {
+      toast({
+        title: _(msg`An unknown error occurred`),
+        variant: 'destructive',
+        description: _(
+          msg`We encountered an unknown error while attempting to update the email blocklist. Please try again later.`,
+        ),
+      });
+    }
+  };
+
+  return (
+    <div>
+      <h2 className="font-semibold">
+        <Trans>Email Blocklist</Trans>
+      </h2>
+      <p className="mt-2 text-muted-foreground text-sm">
+        <Trans>
+          Block signups from additional email domains on top of the bundled disposable email list. Subdomains are
+          matched automatically (e.g. blocking "bad.com" also blocks "foo.bad.com").
+        </Trans>
+      </p>
+
+      <Form {...form}>
+        <form className="mt-4 flex flex-col rounded-md" onSubmit={form.handleSubmit(onBlocklistUpdate)}>
+          <FormField
+            control={form.control}
+            name="enabled"
+            render={({ field }) => (
+              <FormItem>
+                <FormLabel>
+                  <Trans>Enabled</Trans>
+                </FormLabel>
+
+                <FormControl>
+                  <div>
+                    <Switch checked={field.value} onCheckedChange={field.onChange} />
+                  </div>
+                </FormControl>
+              </FormItem>
+            )}
+          />
+
+          <fieldset className="mt-4" disabled={!enabled} aria-disabled={!enabled}>
+            <FormField
+              control={form.control}
+              name="domains"
+              render={({ field }) => (
+                <FormItem>
+                  <FormLabel>
+                    <Trans>Blocked Domains</Trans>
+                  </FormLabel>
+
+                  <FormControl>
+                    <Textarea className="h-32 resize-none" placeholder="bad.com, spam.net, throwaway.io" {...field} />
+                  </FormControl>
+
+                  <FormDescription>
+                    <Trans>Comma-separated list of email domains to block from signing up.</Trans>
+                  </FormDescription>
+
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+          </fieldset>
+
+          <Button type="submit" loading={isUpdateSiteSettingLoading} className="mt-4 justify-end self-end">
+            <Trans>Update Blocklist</Trans>
+          </Button>
+        </form>
+      </Form>
+    </div>
+  );
+};
diff --git a/apps/remix/app/components/general/admin-site-banner-section.tsx b/apps/remix/app/components/general/admin-site-banner-section.tsx
new file mode 100644
index 000000000..b9a140e46
--- /dev/null
+++ b/apps/remix/app/components/general/admin-site-banner-section.tsx
@@ -0,0 +1,197 @@
+import {
+  SITE_SETTINGS_BANNER_ID,
+  type TSiteSettingsBannerSchema,
+  ZSiteSettingsBannerSchema,
+} from '@documenso/lib/server-only/site-settings/schemas/banner';
+import { trpc as trpcReact } from '@documenso/trpc/react';
+import { Button } from '@documenso/ui/primitives/button';
+import { ColorPicker } from '@documenso/ui/primitives/color-picker';
+import {
+  Form,
+  FormControl,
+  FormDescription,
+  FormField,
+  FormItem,
+  FormLabel,
+  FormMessage,
+} from '@documenso/ui/primitives/form/form';
+import { Switch } from '@documenso/ui/primitives/switch';
+import { Textarea } from '@documenso/ui/primitives/textarea';
+import { useToast } from '@documenso/ui/primitives/use-toast';
+import { zodResolver } from '@hookform/resolvers/zod';
+import { msg } from '@lingui/core/macro';
+import { useLingui } from '@lingui/react';
+import { Trans } from '@lingui/react/macro';
+import { useForm } from 'react-hook-form';
+import { useRevalidator } from 'react-router';
+import type { z } from 'zod';
+
+import { useCspNonce } from '~/utils/nonce';
+
+const ZBannerFormSchema = ZSiteSettingsBannerSchema;
+
+type TBannerFormSchema = z.infer<typeof ZBannerFormSchema>;
+
+type AdminSiteBannerSectionProps = {
+  banner: TSiteSettingsBannerSchema | undefined;
+};
+
+export const AdminSiteBannerSection = ({ banner }: AdminSiteBannerSectionProps) => {
+  const nonce = useCspNonce();
+
+  const { toast } = useToast();
+  const { _ } = useLingui();
+  const { revalidate } = useRevalidator();
+
+  const form = useForm<TBannerFormSchema>({
+    resolver: zodResolver(ZBannerFormSchema),
+    defaultValues: {
+      id: SITE_SETTINGS_BANNER_ID,
+      enabled: banner?.enabled ?? false,
+      data: {
+        content: banner?.data?.content ?? '',
+        bgColor: banner?.data?.bgColor ?? '#000000',
+        textColor: banner?.data?.textColor ?? '#FFFFFF',
+      },
+    },
+  });
+
+  const enabled = form.watch('enabled');
+
+  const { mutateAsync: updateSiteSetting, isPending: isUpdateSiteSettingLoading } =
+    trpcReact.admin.updateSiteSetting.useMutation();
+
+  const onBannerUpdate = async ({ id, enabled, data }: TBannerFormSchema) => {
+    try {
+      await updateSiteSetting({
+        id,
+        enabled,
+        data,
+      });
+
+      toast({
+        title: _(msg`Banner Updated`),
+        description: _(msg`Your banner has been updated successfully.`),
+        duration: 5000,
+      });
+
+      await revalidate();
+    } catch (err) {
+      toast({
+        title: _(msg`An unknown error occurred`),
+        variant: 'destructive',
+        description: _(
+          msg`We encountered an unknown error while attempting to update the banner. Please try again later.`,
+        ),
+      });
+    }
+  };
+
+  return (
+    <div>
+      <h2 className="font-semibold">
+        <Trans>Site Banner</Trans>
+      </h2>
+      <p className="mt-2 text-muted-foreground text-sm">
+        <Trans>
+          The site banner is a message that is shown at the top of the site. It can be used to display important
+          information to your users.
+        </Trans>
+      </p>
+
+      <Form {...form}>
+        <form className="mt-4 flex flex-col rounded-md" onSubmit={form.handleSubmit(onBannerUpdate)}>
+          <div className="mt-4 flex flex-col gap-4 md:flex-row">
+            <FormField
+              control={form.control}
+              name="enabled"
+              render={({ field }) => (
+                <FormItem className="flex-1">
+                  <FormLabel>
+                    <Trans>Enabled</Trans>
+                  </FormLabel>
+
+                  <FormControl>
+                    <div>
+                      <Switch checked={field.value} onCheckedChange={field.onChange} />
+                    </div>
+                  </FormControl>
+                </FormItem>
+              )}
+            />
+
+            <fieldset className="flex flex-col gap-4 md:flex-row" disabled={!enabled} aria-disabled={!enabled}>
+              <FormField
+                control={form.control}
+                name="data.bgColor"
+                render={({ field }) => (
+                  <FormItem>
+                    <FormLabel>
+                      <Trans>Background Color</Trans>
+                    </FormLabel>
+
+                    <FormControl>
+                      <div>
+                        <ColorPicker {...field} nonce={nonce} />
+                      </div>
+                    </FormControl>
+
+                    <FormMessage />
+                  </FormItem>
+                )}
+              />
+
+              <FormField
+                control={form.control}
+                name="data.textColor"
+                render={({ field }) => (
+                  <FormItem>
+                    <FormLabel>
+                      <Trans>Text Color</Trans>
+                    </FormLabel>
+
+                    <FormControl>
+                      <div>
+                        <ColorPicker {...field} nonce={nonce} />
+                      </div>
+                    </FormControl>
+
+                    <FormMessage />
+                  </FormItem>
+                )}
+              />
+            </fieldset>
+          </div>
+
+          <fieldset disabled={!enabled} aria-disabled={!enabled}>
+            <FormField
+              control={form.control}
+              name="data.content"
+              render={({ field }) => (
+                <FormItem>
+                  <FormLabel>
+                    <Trans>Content</Trans>
+                  </FormLabel>
+
+                  <FormControl>
+                    <Textarea className="h-32 resize-none" {...field} />
+                  </FormControl>
+
+                  <FormDescription>
+                    <Trans>The content to show in the banner, HTML is allowed</Trans>
+                  </FormDescription>
+
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+          </fieldset>
+
+          <Button type="submit" loading={isUpdateSiteSettingLoading} className="mt-4 justify-end self-end">
+            <Trans>Update Banner</Trans>
+          </Button>
+        </form>
+      </Form>
+    </div>
+  );
+};
diff --git a/apps/remix/app/routes/_authenticated+/admin+/site-settings.tsx b/apps/remix/app/routes/_authenticated+/admin+/site-settings.tsx
index 142cba6fc..ebb454fa2 100644
--- a/apps/remix/app/routes/_authenticated+/admin+/site-settings.tsx
+++ b/apps/remix/app/routes/_authenticated+/admin+/site-settings.tsx
@@ -1,210 +1,36 @@
 import { getSiteSettings } from '@documenso/lib/server-only/site-settings/get-site-settings';
-import {
-  SITE_SETTINGS_BANNER_ID,
-  ZSiteSettingsBannerSchema,
-} from '@documenso/lib/server-only/site-settings/schemas/banner';
-import { trpc as trpcReact } from '@documenso/trpc/react';
-import { Button } from '@documenso/ui/primitives/button';
-import { ColorPicker } from '@documenso/ui/primitives/color-picker';
-import {
-  Form,
-  FormControl,
-  FormDescription,
-  FormField,
-  FormItem,
-  FormLabel,
-  FormMessage,
-} from '@documenso/ui/primitives/form/form';
-import { Switch } from '@documenso/ui/primitives/switch';
-import { Textarea } from '@documenso/ui/primitives/textarea';
-import { useToast } from '@documenso/ui/primitives/use-toast';
-import { zodResolver } from '@hookform/resolvers/zod';
+import { SITE_SETTINGS_BANNER_ID } from '@documenso/lib/server-only/site-settings/schemas/banner';
+import { SITE_SETTINGS_EMAIL_BLOCKLIST_ID } from '@documenso/lib/server-only/site-settings/schemas/email-blocklist';
 import { msg } from '@lingui/core/macro';
 import { useLingui } from '@lingui/react';
-import { Trans } from '@lingui/react/macro';
-import { useForm } from 'react-hook-form';
-import { useRevalidator } from 'react-router';
-import type { z } from 'zod';
 
+import { AdminEmailBlocklistSection } from '~/components/general/admin-email-blocklist-section';
+import { AdminSiteBannerSection } from '~/components/general/admin-site-banner-section';
 import { SettingsHeader } from '~/components/general/settings-header';
-import { useCspNonce } from '~/utils/nonce';
 import type { Route } from './+types/site-settings';
 
-const ZBannerFormSchema = ZSiteSettingsBannerSchema;
-
-type TBannerFormSchema = z.infer<typeof ZBannerFormSchema>;
-
 export async function loader() {
-  const banner = await getSiteSettings().then((settings) =>
-    settings.find((setting) => setting.id === SITE_SETTINGS_BANNER_ID),
-  );
+  const settings = await getSiteSettings();
 
-  return { banner };
+  const banner = settings.find((setting) => setting.id === SITE_SETTINGS_BANNER_ID);
+  const emailBlocklist = settings.find((setting) => setting.id === SITE_SETTINGS_EMAIL_BLOCKLIST_ID);
+
+  return { banner, emailBlocklist };
 }
 
-export default function AdminBannerPage({ loaderData }: Route.ComponentProps) {
-  const { banner } = loaderData;
+export default function AdminSiteSettingsPage({ loaderData }: Route.ComponentProps) {
+  const { banner, emailBlocklist } = loaderData;
 
-  const nonce = useCspNonce();
-
-  const { toast } = useToast();
   const { _ } = useLingui();
-  const { revalidate } = useRevalidator();
-
-  const form = useForm<TBannerFormSchema>({
-    resolver: zodResolver(ZBannerFormSchema),
-    defaultValues: {
-      id: SITE_SETTINGS_BANNER_ID,
-      enabled: banner?.enabled ?? false,
-      data: {
-        content: banner?.data?.content ?? '',
-        bgColor: banner?.data?.bgColor ?? '#000000',
-        textColor: banner?.data?.textColor ?? '#FFFFFF',
-      },
-    },
-  });
-
-  const enabled = form.watch('enabled');
-
-  const { mutateAsync: updateSiteSetting, isPending: isUpdateSiteSettingLoading } =
-    trpcReact.admin.updateSiteSetting.useMutation();
-
-  const onBannerUpdate = async ({ id, enabled, data }: TBannerFormSchema) => {
-    try {
-      await updateSiteSetting({
-        id,
-        enabled,
-        data,
-      });
-
-      toast({
-        title: _(msg`Banner Updated`),
-        description: _(msg`Your banner has been updated successfully.`),
-        duration: 5000,
-      });
-
-      await revalidate();
-    } catch (err) {
-      toast({
-        title: _(msg`An unknown error occurred`),
-        variant: 'destructive',
-        description: _(
-          msg`We encountered an unknown error while attempting to update the banner. Please try again later.`,
-        ),
-      });
-    }
-  };
 
   return (
     <div>
       <SettingsHeader title={_(msg`Site Settings`)} subtitle={_(msg`Manage your site settings here`)} />
 
-      <div className="mt-8">
-        <div>
-          <h2 className="font-semibold">
-            <Trans>Site Banner</Trans>
-          </h2>
-          <p className="mt-2 text-muted-foreground text-sm">
-            <Trans>
-              The site banner is a message that is shown at the top of the site. It can be used to display important
-              information to your users.
-            </Trans>
-          </p>
+      <div className="mt-8 space-y-12">
+        <AdminSiteBannerSection banner={banner} />
 
-          <Form {...form}>
-            <form className="mt-4 flex flex-col rounded-md" onSubmit={form.handleSubmit(onBannerUpdate)}>
-              <div className="mt-4 flex flex-col gap-4 md:flex-row">
-                <FormField
-                  control={form.control}
-                  name="enabled"
-                  render={({ field }) => (
-                    <FormItem className="flex-1">
-                      <FormLabel>
-                        <Trans>Enabled</Trans>
-                      </FormLabel>
-
-                      <FormControl>
-                        <div>
-                          <Switch checked={field.value} onCheckedChange={field.onChange} />
-                        </div>
-                      </FormControl>
-                    </FormItem>
-                  )}
-                />
-
-                <fieldset className="flex flex-col gap-4 md:flex-row" disabled={!enabled} aria-disabled={!enabled}>
-                  <FormField
-                    control={form.control}
-                    name="data.bgColor"
-                    render={({ field }) => (
-                      <FormItem>
-                        <FormLabel>
-                          <Trans>Background Color</Trans>
-                        </FormLabel>
-
-                        <FormControl>
-                          <div>
-                            <ColorPicker {...field} nonce={nonce} />
-                          </div>
-                        </FormControl>
-
-                        <FormMessage />
-                      </FormItem>
-                    )}
-                  />
-
-                  <FormField
-                    control={form.control}
-                    name="data.textColor"
-                    render={({ field }) => (
-                      <FormItem>
-                        <FormLabel>
-                          <Trans>Text Color</Trans>
-                        </FormLabel>
-
-                        <FormControl>
-                          <div>
-                            <ColorPicker {...field} nonce={nonce} />
-                          </div>
-                        </FormControl>
-
-                        <FormMessage />
-                      </FormItem>
-                    )}
-                  />
-                </fieldset>
-              </div>
-
-              <fieldset disabled={!enabled} aria-disabled={!enabled}>
-                <FormField
-                  control={form.control}
-                  name="data.content"
-                  render={({ field }) => (
-                    <FormItem>
-                      <FormLabel>
-                        <Trans>Content</Trans>
-                      </FormLabel>
-
-                      <FormControl>
-                        <Textarea className="h-32 resize-none" {...field} />
-                      </FormControl>
-
-                      <FormDescription>
-                        <Trans>The content to show in the banner, HTML is allowed</Trans>
-                      </FormDescription>
-
-                      <FormMessage />
-                    </FormItem>
-                  )}
-                />
-              </fieldset>
-
-              <Button type="submit" loading={isUpdateSiteSettingLoading} className="mt-4 justify-end self-end">
-                <Trans>Update Banner</Trans>
-              </Button>
-            </form>
-          </Form>
-        </div>
+        <AdminEmailBlocklistSection emailBlocklist={emailBlocklist} />
       </div>
     </div>
   );
diff --git a/packages/auth/server/lib/utils/handle-oauth-callback-url.ts b/packages/auth/server/lib/utils/handle-oauth-callback-url.ts
index ed70d9713..3ab99c9ae 100644
--- a/packages/auth/server/lib/utils/handle-oauth-callback-url.ts
+++ b/packages/auth/server/lib/utils/handle-oauth-callback-url.ts
@@ -5,6 +5,7 @@ import {
   isSignupEnabledForProvider,
 } from '@documenso/lib/constants/auth';
 import { AppError, AppErrorCode } from '@documenso/lib/errors/app-error';
+import { getEmailBlocklistDomains } from '@documenso/lib/server-only/site-settings/get-email-blocklist-domains';
 import { onCreateUserHook } from '@documenso/lib/server-only/user/create-user';
 import { deletedServiceAccountEmail } from '@documenso/lib/server-only/user/service-accounts/deleted-account';
 import { legacyServiceAccountEmail } from '@documenso/lib/server-only/user/service-accounts/legacy-service-account';
@@ -137,7 +138,9 @@ export const handleOAuthCallbackUrl = async (options: HandleOAuthCallbackUrlOpti
   }
 
   // Reject disposable / throwaway email providers for new SSO users.
-  if (isDisposableEmail(email)) {
+  const additionalBlockedDomains = await getEmailBlocklistDomains();
+
+  if (isDisposableEmail(email, additionalBlockedDomains)) {
     const errorUrl = new URL('/signin', NEXT_PUBLIC_WEBAPP_URL());
 
     errorUrl.searchParams.set('error', AuthenticationErrorCode.SignupDisposableEmail);
diff --git a/packages/auth/server/lib/utils/handle-oauth-organisation-callback-url.ts b/packages/auth/server/lib/utils/handle-oauth-organisation-callback-url.ts
index 64a52d118..ff40d4a8b 100644
--- a/packages/auth/server/lib/utils/handle-oauth-organisation-callback-url.ts
+++ b/packages/auth/server/lib/utils/handle-oauth-organisation-callback-url.ts
@@ -1,6 +1,7 @@
 import { sendOrganisationAccountLinkConfirmationEmail } from '@documenso/ee/server-only/lib/send-organisation-account-link-confirmation-email';
 import { isDisposableEmail, isSignupEnabledForProvider } from '@documenso/lib/constants/auth';
 import { AppError } from '@documenso/lib/errors/app-error';
+import { getEmailBlocklistDomains } from '@documenso/lib/server-only/site-settings/get-email-blocklist-domains';
 import { onCreateUserHook } from '@documenso/lib/server-only/user/create-user';
 import { formatOrganisationLoginUrl } from '@documenso/lib/utils/organisation-authentication-portal';
 import { prisma } from '@documenso/prisma';
@@ -75,7 +76,9 @@ export const handleOAuthOrganisationCallbackUrl = async (options: HandleOAuthOrg
     }
 
     // Reject disposable / throwaway email providers for new SSO users.
-    if (isDisposableEmail(email)) {
+    const additionalBlockedDomains = await getEmailBlocklistDomains();
+
+    if (isDisposableEmail(email, additionalBlockedDomains)) {
       const errorUrl = new URL(formatOrganisationLoginUrl(orgUrl));
 
       errorUrl.searchParams.set('error', AuthenticationErrorCode.SignupDisposableEmail);
diff --git a/packages/auth/server/routes/email-password.ts b/packages/auth/server/routes/email-password.ts
index 174fb9d7b..7cf2735cf 100644
--- a/packages/auth/server/routes/email-password.ts
+++ b/packages/auth/server/routes/email-password.ts
@@ -22,6 +22,7 @@ import {
   signupRateLimit,
   verifyEmailRateLimit,
 } from '@documenso/lib/server-only/rate-limit/rate-limits';
+import { getEmailBlocklistDomains } from '@documenso/lib/server-only/site-settings/get-email-blocklist-domains';
 import { createUser } from '@documenso/lib/server-only/user/create-user';
 import { forgotPassword } from '@documenso/lib/server-only/user/forgot-password';
 import { getMostRecentEmailVerificationToken } from '@documenso/lib/server-only/user/get-most-recent-email-verification-token';
@@ -214,7 +215,9 @@ export const emailPasswordRoute = new Hono<HonoAuthContext>()
       });
     }
 
-    if (isDisposableEmail(email)) {
+    const additionalBlockedDomains = await getEmailBlocklistDomains();
+
+    if (isDisposableEmail(email, additionalBlockedDomains)) {
       throw new AppError(AuthenticationErrorCode.SignupDisposableEmail, {
         statusCode: 400,
       });
diff --git a/packages/lib/constants/auth.ts b/packages/lib/constants/auth.ts
index 095bc5101..4768540d4 100644
--- a/packages/lib/constants/auth.ts
+++ b/packages/lib/constants/auth.ts
@@ -132,11 +132,16 @@ export const isEmailDomainAllowedForSignup = (email: string): boolean => {
  * Matching also covers subdomains (e.g. `foo.mailinator.com` resolves to
  * `mailinator.com`).
  *
+ * An optional `additionalBlockedDomains` list can be supplied to layer
+ * admin-configured custom domains on top of the bundled list. These are
+ * matched with the same subdomain-walking behaviour and are expected to be
+ * pre-normalised (trimmed + lowercased) by the caller.
+ *
  * Returns `true` when the email is disposable and should be rejected.
  * Email format validation is intentionally NOT performed here — that is
  * handled by Zod upstream.
  */
-export const isDisposableEmail = (email: string): boolean => {
+export const isDisposableEmail = (email: string, additionalBlockedDomains: string[] = []): boolean => {
   const domain = email.toLowerCase().split('@').pop();
 
   if (!domain) {
@@ -144,11 +149,12 @@ export const isDisposableEmail = (email: string): boolean => {
   }
 
   const blacklist = MailChecker.blacklist();
+  const blocklist = new Set(additionalBlockedDomains);
 
   let currentDomain: string | undefined = domain;
 
   while (currentDomain) {
-    if (blacklist.has(currentDomain)) {
+    if (blacklist.has(currentDomain) || blocklist.has(currentDomain)) {
       return true;
     }
 
diff --git a/packages/lib/server-only/site-settings/get-email-blocklist-domains.ts b/packages/lib/server-only/site-settings/get-email-blocklist-domains.ts
new file mode 100644
index 000000000..b98868233
--- /dev/null
+++ b/packages/lib/server-only/site-settings/get-email-blocklist-domains.ts
@@ -0,0 +1,31 @@
+import { prisma } from '@documenso/prisma';
+
+import { SITE_SETTINGS_EMAIL_BLOCKLIST_ID, ZSiteSettingsEmailBlocklistSchema } from './schemas/email-blocklist';
+
+/**
+ * Returns the list of admin-configured email domains that should be treated as
+ * disposable / blocked, in addition to the bundled `mailchecker` list.
+ *
+ * Returns an empty array when the setting has not been configured, is
+ * disabled, or fails to parse — so a misconfigured setting can never block
+ * signups outright.
+ */
+export const getEmailBlocklistDomains = async (): Promise<string[]> => {
+  const setting = await prisma.siteSettings.findFirst({
+    where: {
+      id: SITE_SETTINGS_EMAIL_BLOCKLIST_ID,
+    },
+  });
+
+  if (!setting || !setting.enabled) {
+    return [];
+  }
+
+  const parsed = ZSiteSettingsEmailBlocklistSchema.safeParse(setting);
+
+  if (!parsed.success) {
+    return [];
+  }
+
+  return parsed.data.data.domains;
+};
diff --git a/packages/lib/server-only/site-settings/schema.ts b/packages/lib/server-only/site-settings/schema.ts
index 02ad09392..85bf75ff8 100644
--- a/packages/lib/server-only/site-settings/schema.ts
+++ b/packages/lib/server-only/site-settings/schema.ts
@@ -1,9 +1,14 @@
 import { z } from 'zod';
 
 import { ZSiteSettingsBannerSchema } from './schemas/banner';
+import { ZSiteSettingsEmailBlocklistSchema } from './schemas/email-blocklist';
 import { ZSiteSettingsTelemetrySchema } from './schemas/telemetry';
 
-export const ZSiteSettingSchema = z.union([ZSiteSettingsBannerSchema, ZSiteSettingsTelemetrySchema]);
+export const ZSiteSettingSchema = z.union([
+  ZSiteSettingsBannerSchema,
+  ZSiteSettingsEmailBlocklistSchema,
+  ZSiteSettingsTelemetrySchema,
+]);
 
 export type TSiteSettingSchema = z.infer<typeof ZSiteSettingSchema>;
 
diff --git a/packages/lib/server-only/site-settings/schemas/email-blocklist.ts b/packages/lib/server-only/site-settings/schemas/email-blocklist.ts
new file mode 100644
index 000000000..46a90b154
--- /dev/null
+++ b/packages/lib/server-only/site-settings/schemas/email-blocklist.ts
@@ -0,0 +1,29 @@
+import { z } from 'zod';
+
+import { ZSiteSettingsBaseSchema } from './_base';
+
+export const SITE_SETTINGS_EMAIL_BLOCKLIST_ID = 'email.blocklist-domains';
+
+/**
+ * Normalises a single domain entry: trims whitespace, lowercases, strips
+ * a leading "@" if present (so users can paste either "bad.com" or "@bad.com").
+ */
+const normaliseDomain = (value: string): string => value.trim().toLowerCase().replace(/^@/, '');
+
+const ZBlocklistDomainsSchema = z
+  .array(z.string())
+  .transform((values) => Array.from(new Set(values.map(normaliseDomain).filter((value) => value.length > 0))));
+
+export const ZSiteSettingsEmailBlocklistSchema = ZSiteSettingsBaseSchema.extend({
+  id: z.literal(SITE_SETTINGS_EMAIL_BLOCKLIST_ID),
+  data: z
+    .object({
+      domains: ZBlocklistDomainsSchema.default([]),
+    })
+    .optional()
+    .default({
+      domains: [],
+    }),
+});
+
+export type TSiteSettingsEmailBlocklistSchema = z.infer<typeof ZSiteSettingsEmailBlocklistSchema>;