Cloudflare Email Forwarding size limit appears to be smaller than Gmail's limit

I’m getting “552 5.3.4 Email data size exceeded” errors for some emails routed through Cloudflare, despite them being small enough to send directly to the email Cloudflare is routing to.

I sent a test email, with just the attachments and none of the text content from an email that failed to send earlier, from my Outlook account to both my Gmail account directly and to my email (which Cloudflare is configured to route to the same gmail account).

The email sent directly to Gmail arrived without error.
The email routed through Cloudflare failed to deliver, with the error “552 5.3.4 Email data size exceeded. PB9GQtUlCN7C”.

The email contained 6 attachments, totaling 21.3 MB in size.

I tried again with 20.0 MB worth of attachments, which got the same error (but different characters at the end of the error message). The headers added by Cloudflare are well under 1.3 MB, so if the email encoding of the attachments was increasing the size enough to hit Gmail’s limit I would’ve expected this to still arrive since the 21.3 MB one sent directly arrived without issue.

I tried again with 18.2 MB worth of attachments, and the email was delivered without an issue.

It would be nice if Cloudflare’s limit could be at least as big as Gmail’s limits.

According to this site the limit is 25mb