Email delivery delays in Microsoft365

One possible reason emails with attachments may be delayed is that Microsoft Defender for Office 365 Safe Attachments scans them twice: before they are sent to EchoMark and again when they return after processing.

If your administrator confirms that repeat scanning is causing the delay, they can configure a mail flow rule to skip Safe Attachments processing on the return trip.

Important: Keep attachment scanning enabled before messages are sent to EchoMark. This exception should apply only to messages returning from EchoMark, not all email or all messages from a particular sender. Have your administrator review the rule’s scope before enabling it.

Configure the mail flow rule

1. In the Exchange admin center, go to Mail flow → Rules and create a new rule.
2. Configure the condition to check for the header x-personalized-for with the value recipient.
3. Configure the action to set a message header:
   • Header: X-MS-Exchange-Organization-SkipSafeAttachmentProcessing
   • Value: 1
4. Place the rule before any rule that uses Stop processing more rules.
5. Save and enable the rule, then test delivery with an attachment.

Still experiencing delays?

Contact EchoMark Support for help reviewing your mail flow configuration.