The message, including attachments, is larger than the receiving server accepts.
Hard bounce · permanent
Common causes
- Large attachments (videos, high-resolution images, PDFs)
- Attachments grow about 33% larger when encoded for email
How to fix it
- Share large files as download links instead of attachments
- Compress images and PDFs
- Keep messages under ~10 MB for broad compatibility
Bounce ExplainerRun the right check for your domain or paste the full bounce message for a precise explanation.
Open Bounce Explainer →Frequently asked questions
What is the maximum email size?
It varies by provider and direction: Gmail and Outlook let you send roughly 20–25 MB per message including encoding, receiving limits differ, and many company servers accept less.