552 5.3.4 Email data size exceeded


An email sent from Gmail and forward by CF to my outlook got following error:
552 5.3.4 Email data size exceeded

Is there a size limit for email? That email was 19MB

The email limit is 25Mb, is 19Mb the entire email size including any attachements?

The email title is in Japanese (8 characters)
Body 1kb
Attachement 1 excel file 19MB

So, whole email is less than 20MB

That’s new…

@sdayman yeah we increased the limit a few days ago to match gmail’s

1 Like

Email encoding adds up to 25% to the size of a message in transit so it is entirely possible the message size exceeds the receiving MTAs limit even if the message storage at rest is below.

Not a specific feature of this Cloudflare service, but of mail generally.

1 Like

@sven2 @cscharff
It is very weird. I tested send by mailgun and 15MB this time, got a another error:
451 Upstream error

“delivery-status”: {
“tls”: true,
mx-host”: “amir.mx.cloudflare.net”,
“code”: 421,
“description”: “”,
“session-seconds”: 95.76113891601562,
“retry-seconds”: 600,
“attempt-no”: 1,
“message”: “451 Upstream error”,
“certificate-verified”: true

Could you please share your domain? Or DM me on the Cloudflare dev discord?

@sven2 My domain is souldraw.jp , But finally mailgun delivered the email by retry, so…It is no problem now I think?

The error you shared is actually due to a timeout when trying to deliver the email to the upstream email server. Which explains why a retry worked.

1 Like