Recently had a customer stop being able to send items to Mimecast with the following\u00a0<\/p>
554 Email rejected due to security policies -\u00a0https:\/\/community.mimecast.com\/docs\/DOC-1369#554<\/a><\/pre>This was happening to Multiple emails and\u00a0Mimecast Logs showed :\u00a0Bounce – Message content not accepted<\/strong><\/p>
Also users trying to email the customer by replying to their email would get the same bounce back<\/p>
So something generic in the content was causing this<\/p>
Generic would be email signatures and Links in email signatures\u00a0are usually the cause, removing one of the domains in the email signature fixed this , we lodged a Support case with Mimecast who removed this domain from their blocklist<\/p>
The actual cause was the company was sending mass emails with using something like mailchimp so it did not have an unsubscribe button so domains in the email were blocked in third party lists like :\u00a0http:\/\/lookup.uribl.com\/<\/p>","protected":false},"excerpt":{"rendered":"
Recently had a customer stop being able to send items to Mimecast with the following\u00a0554 Email rejected due to security policies –\u00a0https:\/\/community.mimecast.com\/docs\/DOC-1369#554This was happening to Multiple emails […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[2483,2484,2482,1797],"class_list":["post-3334","post","type-post","status-publish","format-standard","hentry","category-random","tag-2483","tag-bounce-message-content-not-accepted","tag-email-rejected-due-to-security-policies","tag-mimecast"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t