diff --git a/app/notifications/validators.py b/app/notifications/validators.py
index 91747d14d..745155f39 100644
--- a/app/notifications/validators.py
+++ b/app/notifications/validators.py
@@ -144,10 +144,19 @@ def check_if_service_can_send_to_number(service, number):
         return international_phone_info
 
 
-def check_content_char_count(template_with_content):
+def check_message_is_not_too_long(template_with_content):
     if template_with_content.is_message_too_long():
-        message = f"Text messages cannot be longer than {SMS_CHAR_COUNT_LIMIT} characters. " \
-                  f"Your message is {template_with_content.content_count_without_prefix} characters"
+        message = "Your message is too long."
+        if template_with_content.template_type == SMS_TYPE:
+            message = (
+                f"Text messages cannot be longer than {SMS_CHAR_COUNT_LIMIT} characters. "
+                f"Your message is {template_with_content.content_count_without_prefix} characters long."
+            )
+        elif template_with_content.template_type == EMAIL_TYPE:
+            message = (
+                f"Emails cannot be longer than 1000000 bytes. "
+                f"Your message is {template_with_content.content_size_in_bytes} bytes."
+            )
         raise BadRequestError(message=message)
 
 
@@ -173,7 +182,7 @@ def validate_template(template_id, personalisation, service, notification_type):
 
     check_notification_content_is_not_empty(template_with_content)
 
-    check_content_char_count(template_with_content)
+    check_message_is_not_too_long(template_with_content)
 
     return template, template_with_content
 
diff --git a/requirements-app.txt b/requirements-app.txt
index ded61f2c9..e9d24d4ad 100644
--- a/requirements-app.txt
+++ b/requirements-app.txt
@@ -29,7 +29,7 @@ notifications-python-client==5.7.0
 # PaaS
 awscli-cwlogs>=1.4,<1.5
 
-git+https://github.com/alphagov/notifications-utils.git@43.0.0#egg=notifications-utils==43.0.0
+git+https://github.com/alphagov/notifications-utils.git@43.1.0#egg=notifications-utils==43.1.0
 
 # gds-metrics requires prometheseus 0.2.0, override that requirement as 0.7.1 brings significant performance gains
 prometheus-client==0.8.0
diff --git a/requirements.txt b/requirements.txt
index cae9c641a..244235f30 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -31,7 +31,7 @@ notifications-python-client==5.7.0
 # PaaS
 awscli-cwlogs>=1.4,<1.5
 
-git+https://github.com/alphagov/notifications-utils.git@43.0.0#egg=notifications-utils==43.0.0
+git+https://github.com/alphagov/notifications-utils.git@43.1.0#egg=notifications-utils==43.1.0
 
 # gds-metrics requires prometheseus 0.2.0, override that requirement as 0.7.1 brings significant performance gains
 prometheus-client==0.8.0
@@ -42,14 +42,14 @@ alembic==1.4.3
 amqp==1.4.9
 anyjson==0.3.3
 attrs==20.2.0
-awscli==1.18.164
+awscli==1.18.167
 bcrypt==3.2.0
 billiard==3.3.0.23
 bleach==3.1.4
 blinker==1.4
 boto==2.49.0
 boto3==1.10.38
-botocore==1.19.4
+botocore==1.19.7
 certifi==2020.6.20
 chardet==3.0.4
 click==7.1.2
diff --git a/tests/app/notifications/test_validators.py b/tests/app/notifications/test_validators.py
index de6ce99ce..93727b48f 100644
--- a/tests/app/notifications/test_validators.py
+++ b/tests/app/notifications/test_validators.py
@@ -13,7 +13,7 @@ from app.models import (
 )
 from app.notifications.process_notifications import create_content_for_notification
 from app.notifications.validators import (
-    check_content_char_count,
+    check_message_is_not_too_long,
     check_if_service_can_send_files_by_email,
     check_notification_content_is_not_empty,
     check_service_over_daily_message_limit,
@@ -319,36 +319,51 @@ def test_service_can_send_to_recipient_fails_when_mobile_number_is_not_on_team(s
 @pytest.mark.parametrize('char_count', [612, 0, 494, 200, 918])
 @pytest.mark.parametrize('show_prefix', [True, False])
 @pytest.mark.parametrize('template_type', ['sms', 'email', 'letter'])
-def test_check_content_char_count_passes(notify_db_session, show_prefix, char_count, template_type):
+def test_check_message_is_not_too_long_passes(notify_db_session, show_prefix, char_count, template_type):
     service = create_service(prefix_sms=show_prefix)
     t = create_template(service=service, content='a' * char_count, template_type=template_type)
     template = templates_dao.dao_get_template_by_id_and_service_id(template_id=t.id, service_id=service.id)
     template_with_content = get_template_instance(template=template.__dict__, values={})
-    assert check_content_char_count(template_with_content) is None
+    assert check_message_is_not_too_long(template_with_content) is None
 
 
 @pytest.mark.parametrize('char_count', [919, 6000])
 @pytest.mark.parametrize('show_prefix', [True, False])
-def test_check_content_char_count_fails(notify_db_session, show_prefix, char_count):
+def test_check_message_is_not_too_long_for_too_long_sms_messages(notify_db_session, show_prefix, char_count):
     with pytest.raises(BadRequestError) as e:
         service = create_service(prefix_sms=show_prefix)
         t = create_template(service=service, content='a' * char_count, template_type='sms')
         template = templates_dao.dao_get_template_by_id_and_service_id(template_id=t.id, service_id=service.id)
         template_with_content = get_template_instance(template=template.__dict__, values={})
-        check_content_char_count(template_with_content)
+        check_message_is_not_too_long(template_with_content)
     assert e.value.status_code == 400
     assert e.value.message == f'Text messages cannot be longer than {SMS_CHAR_COUNT_LIMIT} characters. ' \
-                              f'Your message is {char_count} characters'
+                              f'Your message is {char_count} characters long.'
+    assert e.value.fields == []
+
+
+def test_check_message_is_not_too_long_for_too_big_email_messages(notify_db_session):
+    with pytest.raises(BadRequestError) as e:
+        service = create_service()
+        t = create_template(service=service, content='a' * 1000000, template_type='email')
+        template = templates_dao.dao_get_template_by_id_and_service_id(template_id=t.id, service_id=service.id)
+        template_with_content = get_template_instance(template=template.__dict__, values={})
+        check_message_is_not_too_long(template_with_content)
+    assert e.value.status_code == 400
+    assert e.value.message == (
+        f"Emails cannot be longer than 1000000 bytes. "
+        f"Your message is 1000081 bytes."
+    )
     assert e.value.fields == []
 
 
 @pytest.mark.parametrize('template_type', ['email', 'letter'])
-def test_check_content_char_count_passes_for_long_email_or_letter(sample_service, template_type):
+def test_check_message_is_not_too_long_passes_for_long_email_or_letter(sample_service, template_type):
     t = create_template(service=sample_service, content='a' * 1000, template_type=template_type)
     template = templates_dao.dao_get_template_by_id_and_service_id(template_id=t.id,
                                                                    service_id=t.service_id)
     template_with_content = get_template_instance(template=template.__dict__, values={})
-    assert check_content_char_count(template_with_content) is None
+    assert check_message_is_not_too_long(template_with_content) is None
 
 
 def test_check_notification_content_is_not_empty_passes(notify_api, mocker, sample_service):
@@ -394,7 +409,7 @@ def test_validate_template_calls_all_validators(mocker, fake_uuid, sample_servic
         'app.notifications.validators.create_content_for_notification', return_value="content"
     )
     mock_check_not_empty = mocker.patch('app.notifications.validators.check_notification_content_is_not_empty')
-    mock_check_message_is_too_long = mocker.patch('app.notifications.validators.check_content_char_count')
+    mock_check_message_is_too_long = mocker.patch('app.notifications.validators.check_message_is_not_too_long')
     template, template_with_content = validate_template(template.id, {}, sample_service, "email")
 
     mock_check_type.assert_called_once_with("email", "email")
diff --git a/tests/app/service/test_send_one_off_notification.py b/tests/app/service/test_send_one_off_notification.py
index 2f6e1ee60..cfc025157 100644
--- a/tests/app/service/test_send_one_off_notification.py
+++ b/tests/app/service/test_send_one_off_notification.py
@@ -318,7 +318,7 @@ def test_send_one_off_notification_raises_if_message_too_long(persist_mock, noti
         send_one_off_notification(service.id, post_data)
 
     assert e.value.message == f'Text messages cannot be longer than {SMS_CHAR_COUNT_LIMIT} characters. ' \
-                              f'Your message is {1029} characters'
+                              f'Your message is {1029} characters long.'
 
 
 def test_send_one_off_notification_fails_if_created_by_other_service(sample_template):