Re: [ext] Re: Panic: file smtp-address.c: line 530 (smtp_address_write): assertion failed: (smtp_char_is_qpair(*p))

1. Who or what is sending messages like that (without the proper capability support available at the server side)?

I think that was some sort of commercial mass mailer:

List-Unsubscribe: <http://newsletter.jomec.de/rmftlp.php?cid=...>

2. Why would an MTA accept this message? What software is doing that (and why)?

Postfix. It was just in the headers, so it was not relevvant for delivery.

3. What does the envelope address look like? Do both header and envelope have that umlaut (unlikely, because Dovecot should reject that already)? Maybe this could be fixed by substituting the envelope address if it is sufficiently similar.

Envelope sender is: bounce+15396@bounce.crsend.com

4. Where does this fail actually? At some point it is trying to construct an SMTP (RFC 5321) address from the header address (RFC 5322). Do you have a GDB backtrace with proper symbols?

Don't have a backtrace yet, but since the mail is still in the queue I could try getting one.

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