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E-Mail Delivery Issues

Why is my email with an attachment not being received?

There could be several reasons for this issue:

  • Microsoft 365 has a 150MB size limit for sending and receiving emails. If your attachment exceeds these limits, the message may be rejected.
  • Specific transport rules in your organization or the recipient's organization could block or restrict emails with large attachments for security or policy reasons.
  • You are sending a prohibited file type, such as executables or macro-enabled Office files.

I believe that my e-mails are being rejected or marked as junk by the recipient. What should I do?

  • If you received a Non-Delivery Report (NDR) message, please forward that to our helpdesk at support@enstep.com.
  • In case your messages are being marked as junk, we recommend reaching out to the recipient and asking for his e-mail administrator contact. Then, submit a ticket to our helpdesk with the recipient's e-mail address, the subject and send date/time for the message that got marked as junk, and their IT contact. We will work with them to get you whitelisted.

Are there restrictions on certain file types or attachments in Exchange Online?

Yes. Executable files (such as .exe, .cmd, .ps1, .bat, .vbs, .sh) are prohibited. Macro-enabled Office files (such as .docm, .xlsm, .pptm) are restricted as well.

What alternatives exist for sending or receiving large attachements?

We recommend using OneDrive for sharing large attachments. Please follow this guide for sharing files. If you need to request files from a recipient, follow this guide.