🪲: Headers and body stripped from mail delivery subsystem failure notifications

[kosmavision]

What happened?

All headers other than DKIM-Signature, To, From, Message-Id, and Date are being stripped from the original rfc822 message attached to delivery failure notifications. The body is also being stripped.

I also noticed that in some cases, in the attached rfc822 message the To header is stripped, while in other cases the From header is removed.

This makes any sort of automated bounce processing difficult. Is there a configuration option I'm missing somewhere that controls this?

How can we reproduce the problem?

I can reproduce the problem by doing the following steps:

Sending email with custom X-headers to a non-existent domain.

Version

v0.14.x

What database are you using?

RocksDB

What blob storage are you using?

RocksDB

Where is your directory located?

None

What operating system are you using?

Linux

Relevant log output

Code of Conduct

• I agree to follow this project's Code of Conduct

[kosmavision]

Reopening this after more testing with different types of email messages (plain text, multipart, many headers, few headers). There is definitely a bug with how the rfc822 attachments to bounce notifications are processed. The headers included here actually vary almost randomly. Two messages with different contents but exactly the same headers will be attached containing different sets of headers. Sometimes one or two custom headers are preserved. Other times the To, From, or Subject header gets stripped.

[kosmavision]

This appears to be due to the default Stalwart inclusion of both RSA and and ED25519 dkim signatures. Having both seems to use up the available character limit (arbitrary?) for the rfc822 attachment of the bounced email, which randomly causes headers to disappear or even corruption of headers that do get included (such as Subject being truncated or mixed with part of the To address, etc). After removing ED25519 signing, the problem seems to be resolved. But keeping open as definitely unexpected buggy behavior.