Maximum email attachment size

The maximum size of one complete email message is 75 MB. This limit includes the message body, technical headers and every encoded attachment. Encoding can increase a file's size by roughly one third during transmission.

Practical guidance

• Keep an individual attachment comfortably below 50 MB where possible.
• Account for a lower limit at the recipient's email provider; many external services accept considerably less than 75 MB.
• Compress multiple files into a zip archive if this meaningfully reduces the total size.
• Share large or sensitive files through an appropriate file-sharing service with access controls and an expiry date.

For large files, consider WeTransfer, Dropbox, OneDrive or a secure customer portal. Before sending, check whether the file contains personal data or confidential business information and choose a method that meets the required level of security.

If sending fails

Remove the attachment and send a test message without it. If that succeeds, reduce the file size or send a secure download link. For a persistent error, record the file size, file type, recipient and exact error message.