diff --git a/app/views/account/SubscriptionView.coffee b/app/views/account/SubscriptionView.coffee
index de796e5e2..41ace9c30 100644
--- a/app/views/account/SubscriptionView.coffee
+++ b/app/views/account/SubscriptionView.coffee
@@ -89,7 +89,7 @@ module.exports = class SubscriptionView extends RootView
   onClickRecipientsSubscribe: (e) ->
     emails = @$el.find('.recipient-emails').val().split('\n')
     valid = @emailValidator.validateEmails(emails, =>@render?())
-    @recipientSubs.startSubscribe(emails) if valid 
+    @recipientSubs.startSubscribe(emails) if valid
 
   onClickRecipientUnsubscribe: (e) ->
     $(e.target).addClass('hide')
@@ -108,8 +108,8 @@ class EmailValidator
 
   validateEmails: (emails, render) ->
     @lastEmails = emails.join('\n')
-    #taken from http://www.regular-expressions.info/email.html 
-    emailRegex = /[A-z0-9._%+-]+@[A-z0-9.-]+\.[A-z]{2,4}/
+    #taken from http://www.regular-expressions.info/email.html
+    emailRegex = /[A-z0-9._%+-]+@[A-z0-9.-]+\.[A-z]{2,63}/
     @validEmails = (email for email in emails when emailRegex.test(email.trim().toLowerCase()))
     return @emailsInvalid(render) if @validEmails.length < emails.length
     return @emailsValid(render)
diff --git a/app/views/core/AuthModal.coffee b/app/views/core/AuthModal.coffee
index 10494a36f..e7e73f0e7 100644
--- a/app/views/core/AuthModal.coffee
+++ b/app/views/core/AuthModal.coffee
@@ -79,7 +79,7 @@ module.exports = class AuthModal extends ModalView
 
   emailCheck: ->
     email = $('#email', @$el).val()
-    filter = /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i  # https://news.ycombinator.com/item?id=5763990
+    filter = /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,63}$/i  # https://news.ycombinator.com/item?id=5763990
     unless filter.test(email)
       forms.setErrorToProperty @$el, 'email', 'Please enter a valid email address', true
       return false
diff --git a/app/views/courses/StudentSignUpModal.coffee b/app/views/courses/StudentSignUpModal.coffee
index 5e4ec404c..3b7c03e12 100644
--- a/app/views/courses/StudentSignUpModal.coffee
+++ b/app/views/courses/StudentSignUpModal.coffee
@@ -37,7 +37,7 @@ module.exports = class StudentSignUpModal extends ModalView
 
   emailCheck: ->
     email = @$('#email').val()
-    filter = /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i  # https://news.ycombinator.com/item?id=5763990
+    filter = /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,63}$/i  # https://news.ycombinator.com/item?id=5763990
     unless filter.test(email)
       @$('#errors-alert').text($.i18n.t('share_progress_modal.email_invalid')).removeClass('hide')
       return false