What is the standard email size limit?

Most consumer providers like Gmail and Outlook allow up to 25MB. However, Base64 encoding for attachments increases their size by ~33%, so a 20MB file might exceed the limit.

Does this affect my sender reputation?

No, size limit bounces do not typically harm your reputation, but they do prevent your message from being delivered.

← Error library

552 5.3.4 Message too big

permanent Content

Meaning

The message was rejected because its total size (including attachments and headers) exceeds the receiving server's maximum allowed size.

Common causes

You attached files that are too large (e.g., over 25MB for Gmail).
The email contains massive inline images or excessive HTML code.
The message headers are abnormally large.

How to fix

Remove large attachments and instead host the files on a cloud service (like Google Drive or AWS S3) and link to them in the email.
Optimize and compress inline images.
Ensure your email complies with standard size limits (usually 25MB, but sometimes smaller for corporate servers).

Provider notes

Gmail. Returns 'Your message exceeded Google's message size limits.'

Example bounce

552 5.3.4 Your message exceeded Google's message size limits.

FAQ

What is the standard email size limit?: Most consumer providers like Gmail and Outlook allow up to 25MB. However, Base64 encoding for attachments increases their size by ~33%, so a 20MB file might exceed the limit.
Does this affect my sender reputation?: No, size limit bounces do not typically harm your reputation, but they do prevent your message from being delivered.