diff --git a/designer/server/src/routes/forms/contact/email.js b/designer/server/src/routes/forms/contact/email.js
index c3ae981794..973bb158c9 100644
--- a/designer/server/src/routes/forms/contact/email.js
+++ b/designer/server/src/routes/forms/contact/email.js
@@ -1,6 +1,7 @@
 import {
   Scopes,
-  emailAddressSchema,
+  UNICODE_EMAIL_ERROR_MESSAGE,
+  emailAddressNoUnicodeSchema,
   emailResponseTimeSchema
 } from '@defra/forms-model'
 import { StatusCodes } from 'http-status-codes'
@@ -20,13 +21,14 @@ export const ROUTE_PATH_EDIT_EMAIL_CONTACT =
   '/library/{slug}/edit/contact/email'
 
 export const emailContactSchema = Joi.object().keys({
-  address: emailAddressSchema
+  address: emailAddressNoUnicodeSchema
     .required()
     .when('_delete', { is: true, then: Joi.allow('') })
     .messages({
       'string.empty': 'Enter an email address for dedicated support',
       'string.email':
-        'Enter an email address for dedicated support in the correct format'
+        'Enter an email address for dedicated support in the correct format',
+      'string.unicode': UNICODE_EMAIL_ERROR_MESSAGE
     }),
   responseTime: emailResponseTimeSchema
     .required()
diff --git a/designer/server/src/routes/forms/create.js b/designer/server/src/routes/forms/create.js
index 054ec9675b..75e1b667dc 100644
--- a/designer/server/src/routes/forms/create.js
+++ b/designer/server/src/routes/forms/create.js
@@ -1,5 +1,6 @@
 import {
   Scopes,
+  UNICODE_EMAIL_ERROR_MESSAGE,
   getErrorMessage,
   organisationSchema,
   slugify,
@@ -41,7 +42,8 @@ export const schema = Joi.object().keys({
   }),
   teamEmail: teamEmailSchema.messages({
     'string.empty': 'Enter a shared team email address',
-    'string.email': 'Enter a shared team email address in the correct format'
+    'string.email': 'Enter a shared team email address in the correct format',
+    'string.unicode': UNICODE_EMAIL_ERROR_MESSAGE
   })
 })
 
diff --git a/designer/server/src/routes/forms/notification-email.js b/designer/server/src/routes/forms/notification-email.js
index 71d8492805..b5529b24a0 100644
--- a/designer/server/src/routes/forms/notification-email.js
+++ b/designer/server/src/routes/forms/notification-email.js
@@ -1,4 +1,8 @@
-import { Scopes, notificationEmailAddressSchema } from '@defra/forms-model'
+import {
+  Scopes,
+  UNICODE_EMAIL_ERROR_MESSAGE,
+  notificationEmailAddressSchema
+} from '@defra/forms-model'
 import { StatusCodes } from 'http-status-codes'
 import Joi from 'joi'
 
@@ -21,7 +25,8 @@ export const schema = Joi.object().keys({
   notificationEmail: notificationEmailAddressSchema.required().messages({
     'string.empty': EMPTY_MESSAGE,
     'string.email': INCORRECT_FORMAT_MESSAGE,
-    'string.pattern.base': INCORRECT_FORMAT_MESSAGE
+    'string.pattern.base': INCORRECT_FORMAT_MESSAGE,
+    'string.unicode': UNICODE_EMAIL_ERROR_MESSAGE
   })
 })
 
diff --git a/designer/server/src/routes/manage/user.js b/designer/server/src/routes/manage/user.js
index 2d8ec46591..3e622059da 100644
--- a/designer/server/src/routes/manage/user.js
+++ b/designer/server/src/routes/manage/user.js
@@ -1,4 +1,9 @@
-import { Roles, Scopes } from '@defra/forms-model'
+import {
+  Roles,
+  Scopes,
+  UNICODE_EMAIL_ERROR_MESSAGE,
+  emailAddressNoUnicodeSchema
+} from '@defra/forms-model'
 import Boom from '@hapi/boom'
 import { StatusCodes } from 'http-status-codes'
 import Joi from 'joi'
@@ -15,11 +20,10 @@ import * as userService from '~/src/services/userService.js'
 const errorKey = sessionNames.validationFailure.manageUsers
 
 const addUserSchema = Joi.object({
-  emailAddress: Joi.string()
-    .email()
-    .trim()
+  emailAddress: emailAddressNoUnicodeSchema
     .required()
     .messages({
+      'string.unicode': UNICODE_EMAIL_ERROR_MESSAGE,
       '*': 'Enter an email address in the correct format'
     })
     .description('Email address of user'),
diff --git a/model/src/form/form-audit/index.ts b/model/src/form/form-audit/index.ts
index 8c9cd76bab..308b82a033 100644
--- a/model/src/form/form-audit/index.ts
+++ b/model/src/form/form-audit/index.ts
@@ -52,9 +52,9 @@ import {
   type FormUploadedMessageData,
   type FormsBackupRequestedMessageData
 } from '~/src/form/form-audit/types.js'
+import { emailAddressNoUnicodeSchema } from '~/src/form/form-editor/index.js'
 import {
   contactSchema,
-  emailAddressSchema,
   emailResponseTimeSchema,
   idSchema,
   notificationEmailAddressSchema,
@@ -181,7 +181,7 @@ export const formSupportOnlineChanges = Joi.object<FormSupportOnlineChanges>()
 
 export const formSupportEmailChanges = Joi.object<FormSupportEmailChanges>()
   .keys({
-    address: emailAddressSchema.optional(),
+    address: emailAddressNoUnicodeSchema.optional(),
     responseTime: emailResponseTimeSchema.optional()
   })
   .description('Changes schema for FORM_SUPPORT_EMAIL_UPDATED event')
@@ -238,7 +238,7 @@ export const entitlementMessageData = Joi.object<EntitlementMessageData>().keys(
   {
     userId: Joi.string().required(),
     displayName: Joi.string().required(),
-    email: Joi.string().email().required(),
+    email: emailAddressNoUnicodeSchema.required(),
     roles: Joi.array().items(Joi.string())
   }
 )
@@ -260,7 +260,7 @@ export const excelGenerationMessageData =
     .keys({
       formId: Joi.string().required(),
       formName: Joi.string().required(),
-      notificationEmail: Joi.string().email().required()
+      notificationEmail: emailAddressNoUnicodeSchema.required()
     })
     .required()
     .description(
diff --git a/model/src/form/form-definition/constants.ts b/model/src/form/form-definition/constants.ts
new file mode 100644
index 0000000000..b0be34eb6c
--- /dev/null
+++ b/model/src/form/form-definition/constants.ts
@@ -0,0 +1,2 @@
+export const MIN_NUMBER_OF_REPEAT_ITEMS = 1
+export const MAX_NUMBER_OF_REPEAT_ITEMS = 200
diff --git a/model/src/form/form-definition/index.ts b/model/src/form/form-definition/index.ts
index a780f60708..2a5cace512 100644
--- a/model/src/form/form-definition/index.ts
+++ b/model/src/form/form-definition/index.ts
@@ -25,6 +25,10 @@ import {
   type RelativeDateValueData,
   type RelativeDateValueDataV2
 } from '~/src/conditions/types.js'
+import {
+  MAX_NUMBER_OF_REPEAT_ITEMS,
+  MIN_NUMBER_OF_REPEAT_ITEMS
+} from '~/src/form/form-definition/constants.js'
 import {
   isConditionListItemRefValueData,
   isFormDefinition
@@ -47,6 +51,7 @@ import {
   type RepeatSchema,
   type Section
 } from '~/src/form/form-definition/types.js'
+import { emailAddressNoUnicodeSchema } from '~/src/form/form-editor/index.js'
 import { checkErrors } from '~/src/form/form-manager/errors.js'
 import {
   FormDefinitionError,
@@ -348,9 +353,6 @@ const conditionSchema = Joi.object<ConditionData>()
       )
   })
 
-export const MIN_NUMBER_OF_REPEAT_ITEMS = 1
-export const MAX_NUMBER_OF_REPEAT_ITEMS = 200
-
 export const conditionDataSchemaV2 = Joi.object<ConditionDataV2>()
   .description('Condition definition')
   .keys({
@@ -1041,13 +1043,7 @@ const feedbackSchema = Joi.object<FormDefinition['feedback']>()
       .description(
         'URL to an external feedback form when not using built-in feedback'
       ),
-    emailAddress: Joi.string()
-      .trim()
-      .email({
-        tlds: {
-          allow: false
-        }
-      })
+    emailAddress: emailAddressNoUnicodeSchema
       .optional()
       .description('Email address where feedback is sent')
   })
@@ -1155,8 +1151,7 @@ export const formDefinitionSchema = Joi.object<FormDefinition>()
       .optional()
       .description('Phase banner configuration'),
     options: optionsSchema.optional().description('Options for the form'),
-    outputEmail: Joi.string()
-      .trim()
+    outputEmail: emailAddressNoUnicodeSchema
       .email({ tlds: { allow: ['uk'] } })
       .optional()
       .description('Email address where form submissions are sent'),
@@ -1165,8 +1160,7 @@ export const formDefinitionSchema = Joi.object<FormDefinition>()
       .description('Configuration for submission output format'),
     outputs: Joi.array()
       .items({
-        emailAddress: Joi.string()
-          .trim()
+        emailAddress: emailAddressNoUnicodeSchema
           .email({ tlds: { allow: ['uk'] } })
           .description('Email address where form submissions are sent'),
         audience: Joi.string()
@@ -1244,6 +1238,11 @@ export const formDefinitionV2Schema = formDefinitionSchema
   })
   .description('Form definition schema for V2')
 
+export {
+  MAX_NUMBER_OF_REPEAT_ITEMS,
+  MIN_NUMBER_OF_REPEAT_ITEMS
+} from '~/src/form/form-definition/constants.js'
+
 // Maintain compatibility with legacy named export
 // E.g. `import { Schema } from '@defra/forms-model'`
 export const Schema = formDefinitionSchema
diff --git a/model/src/form/form-editor/index.ts b/model/src/form/form-editor/index.ts
index 90ab711cdd..65d6480c76 100644
--- a/model/src/form/form-editor/index.ts
+++ b/model/src/form/form-editor/index.ts
@@ -5,7 +5,7 @@ import { ComponentType } from '~/src/components/enums.js'
 import {
   MAX_NUMBER_OF_REPEAT_ITEMS,
   MIN_NUMBER_OF_REPEAT_ITEMS
-} from '~/src/form/form-definition/index.js'
+} from '~/src/form/form-definition/constants.js'
 import {
   type FormEditorInputCheckAnswersSettings,
   type FormEditorInputPage,
@@ -16,6 +16,16 @@ import {
   type GovukFieldUsePostcodeLookup,
   type GovukStringField
 } from '~/src/form/form-editor/types.js'
+import { preventUnicodeInEmail } from '~/src/form/utils/prevent-unicode.js'
+
+export const emailAddressNoUnicodeSchema = Joi.string()
+  .trim()
+  .email()
+  .custom((value, helpers) => preventUnicodeInEmail(value, helpers))
+  .description('Email address preventing unicode characters')
+
+export const UNICODE_EMAIL_ERROR_MESSAGE =
+  'The email address you entered includes invalid characters, for example, long dashes'
 
 export enum QuestionTypeSubGroup {
   WrittenAnswerSubGroup = 'writtenAnswerSub',
diff --git a/model/src/form/form-metadata/index.ts b/model/src/form/form-metadata/index.ts
index d3e5e818d3..36182bcd6f 100644
--- a/model/src/form/form-metadata/index.ts
+++ b/model/src/form/form-metadata/index.ts
@@ -1,5 +1,6 @@
 import Joi from 'joi'
 
+import { emailAddressNoUnicodeSchema } from '~/src/form/form-editor/index.js'
 import {
   type FormMetadata,
   type FormMetadataAuthor,
@@ -53,7 +54,7 @@ export const teamNameSchema = Joi.string()
   .required()
   .description('Name of the team responsible for the form')
 
-export const teamEmailSchema = Joi.string()
+export const teamEmailSchema = emailAddressNoUnicodeSchema
   .email({ tlds: { allow: ['uk'] } })
   .trim()
   .required()
@@ -63,9 +64,7 @@ export const phoneSchema = Joi.string()
   .trim()
   .description('Phone number for form-related inquiries')
 
-export const emailAddressSchema = Joi.string()
-  .email()
-  .trim()
+export const emailAddressSchema = emailAddressNoUnicodeSchema
   .required()
   .description('Email address for form-related inquiries')
 
@@ -132,10 +131,10 @@ export const termsAndConditionsAgreedSchema = Joi.boolean().description(
   'Whether the data protection terms and conditions have been agreed to'
 )
 
-export const notificationEmailAddressSchema = Joi.string()
-  .email()
-  .trim()
-  .description('Email address to receive form submission notifications')
+export const notificationEmailAddressSchema =
+  emailAddressNoUnicodeSchema.description(
+    'Email address to receive form submission notifications'
+  )
 
 export const authoredAtSchema = Joi.date()
   .iso()
diff --git a/model/src/form/utils/index.ts b/model/src/form/utils/index.ts
index c95d0f404d..fac55e1deb 100644
--- a/model/src/form/utils/index.ts
+++ b/model/src/form/utils/index.ts
@@ -1,2 +1,3 @@
 export { findStartPage } from '~/src/form/utils/find-start-page.js'
 export { findDefinitionListFromComponent } from '~/src/form/utils/list.js'
+export { preventUnicodeInEmail } from '~/src/form/utils/prevent-unicode.js'
diff --git a/model/src/form/utils/prevent-unicode.js b/model/src/form/utils/prevent-unicode.js
new file mode 100644
index 0000000000..415f3ad694
--- /dev/null
+++ b/model/src/form/utils/prevent-unicode.js
@@ -0,0 +1,19 @@
+/**
+ * Custom Joi validator to prevent Unicode characters in say an email address.
+ * Although Joi has Joi.email({ allowUnicode: false }), we can't differentiate from a general
+ * email format error or a Unicode error - hance the custom validator to allow a different error message
+ * @param {unknown} value
+ * @param {CustomHelpers<string>} helpers
+ */
+export function preventUnicodeInEmail(value, helpers) {
+  if (!value || typeof value !== 'string') {
+    return helpers.error('string.empty')
+  }
+  const invalidCharsRegex = /[^a-zA-Z0-9.!#$%&'*+/=?^_`{|}~@-]/
+  const invalid = invalidCharsRegex.exec(value)
+  return invalid ? helpers.error('string.unicode') : value
+}
+
+/**
+ * @import { type CustomHelpers } from 'joi'
+ */
diff --git a/model/src/form/utils/prevent-unicode.test.js b/model/src/form/utils/prevent-unicode.test.js
new file mode 100644
index 0000000000..5ec0663151
--- /dev/null
+++ b/model/src/form/utils/prevent-unicode.test.js
@@ -0,0 +1,44 @@
+import { preventUnicodeInEmail } from '~/src/form/utils/prevent-unicode.js'
+
+describe('preventUnicodeInEmail', () => {
+  const mockHelpers = {
+    error: jest.fn()
+  }
+
+  beforeEach(() => {
+    jest.clearAllMocks()
+  })
+
+  it('should handle undefined', () => {
+    // @ts-expect-error - partial helper mock
+    preventUnicodeInEmail(undefined, mockHelpers)
+    expect(mockHelpers.error).toHaveBeenCalledWith('string.empty')
+  })
+
+  it('should handle not a string', () => {
+    // @ts-expect-error - partial helper mock
+    preventUnicodeInEmail({ abc: 123 }, mockHelpers)
+    expect(mockHelpers.error).toHaveBeenCalledWith('string.empty')
+  })
+
+  it.each([
+    'first.last@domain.co.uk',
+    'first-last@domain.uk',
+    'only@domain.uk'
+  ])('handles a valid emails', (/** @type {string} */ email) => {
+    // @ts-expect-error - partial helper mock
+    expect(preventUnicodeInEmail(email, mockHelpers)).toBe(email)
+    expect(mockHelpers.error).not.toHaveBeenCalled()
+  })
+
+  const enDash = '\u2013'
+  const emDash = '\u2014'
+  it.each([`first${enDash}last@domain.co.uk`, `first${emDash}}last@domain.uk`])(
+    'handles an invalid email',
+    (/** @type {string} */ email) => {
+      // @ts-expect-error - partial helper mock
+      preventUnicodeInEmail(email, mockHelpers)
+      expect(mockHelpers.error).toHaveBeenCalledWith('string.unicode')
+    }
+  )
+})
diff --git a/package-lock.json b/package-lock.json
index 1c1450fb2f..d0495dd45e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -29623,15 +29623,6 @@
       "integrity": "sha512-pcaShQc1Shq0y+E7GqJqvZj8DTthWV1KeHGdi0Z6IAin2Oi3JnLCOfwnCo84qc+HAp52wT9nK9H7FAJp5a44GQ==",
       "license": "ISC"
     },
-    "node_modules/preact": {
-      "version": "8.5.3",
-      "resolved": "https://registry.npmjs.org/preact/-/preact-8.5.3.tgz",
-      "integrity": "sha512-O3kKP+1YdgqHOFsZF2a9JVdtqD+RPzCQc3rP+Ualf7V6rmRDchZ9MJbiGTT7LuyqFKZqlHSOyO/oMFmI2lVTsw==",
-      "hasInstallScript": true,
-      "license": "MIT",
-      "optional": true,
-      "peer": true
-    },
     "node_modules/prelude-ls": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.2.1.tgz",