- You receive a non-delivery report (NDR) that states that the message is too large (NDR code 5.2.1 or 5.2.3).
- The sender does not receive an NDR.
- A message size limitation is set on the sender’s mailbox, or a limitation policy is set on the sender’s email server.
- A message size limitation is set on the recipient’s email server.
- Use compression technology, such as WinZip.
- Split the attachment into multiple files that can be sent separately.
- Use other technologies such as FTP or Internet File Sharing (such as OneDrive) to share or transport large files that do not require high security or data encryption.
- Message subject
- SMTP sender/recipient
- Date/time sent
Or, contact Microsoft Online Services Support by telephone .