Fix
Gmail says 'message is too large'
Gmail rejects an outbound message above 25 MB total size and an inbound message above 50 MB. Base64 encoding inflates an attachment by roughly 33 per cent, so a 20 MB file already exceeds the 25 MB send ceiling once headers and encoding are counted.
| Send ceiling | 25 MB total message size, encoding included |
|---|---|
| Receive ceiling | 50 MB total message size |
| Encoding overhead | Attachments inflate by roughly 33 per cent in transit |
| Drive fallback | Files above the ceiling are auto-converted to a Drive link |
| Gateway variance | A recipient's own gateway may cap lower than 50 MB |
Why a 20 MB file fails a 25 MB limit
Gmail measures the encoded message, not the file on disk. Attachments are base64 encoded for transport, which adds about a third to their size, so a 20 MB attachment arrives at the ceiling as roughly 27 MB and is rejected before it leaves the tenant.
The same arithmetic explains inbound failures that look inconsistent. A sender on a system that reports raw file size will insist the file was under the limit, while the receiving gateway counted the encoded message and refused it.
The three fixes, in the order to try them
First, let Gmail insert a Drive link instead of an attachment; sharing permission travels with the link and the message drops to a few kilobytes. Second, compress or split the file if the recipient genuinely needs a copy rather than access.
Third, if this recurs for a whole team, the problem is a workflow sending large files by mail at all. Moving that exchange to a shared drive with external members removes the ceiling and gives you an audit trail the mailbox never had.
- Attach from Drive rather than from disk for anything above 10 MB.
- Check the recipient gateway's own cap before assuming 50 MB applies.
- Watch for scanners and archivers that re-encode and re-inflate a message in transit.
What we see that others don't say
Because base64 encoding inflates payloads by about a third, the practical attachment ceiling in Gmail is closer to 18 MB on disk than the 25 MB figure the documentation quotes, which is why files that look compliant still bounce.
What this doesn't cover
- Google Groups and some mailing lists apply their own lower size caps that this page does not cover.
- Third-party mail security gateways can reject below Gmail's ceiling; the bounce text names the rejecting host.
Questions we get asked
- What is Gmail's maximum attachment size?
- 25 MB for a message you send and 50 MB for a message you receive, measured on the encoded message. Because encoding adds about a third, plan for a practical attachment ceiling near 18 MB.
- Does a Drive link count towards the limit?
- No. A Drive link is a few hundred bytes of text, so message size stops being the constraint. The constraint becomes sharing permission, which is why link attachments sometimes reach recipients who cannot open them.
How this page is verified
Reviewed by Pearl Lemon Cloud migrations desk, Google Workspace migration engineers. Last checked .
- Ceilings checked against Google's published Gmail sending limits at the review date.
- Encoding overhead confirmed by comparing on-disk and encoded message size for a 20 MB test attachment.
Sources you can check
Related pages
Large-file email failing across a whole team?
We rework the workflow onto shared drives with external access, so the size ceiling stops being a daily support ticket.