Currently e-mail sent to lists is refused if it only contains Cc: headers and no To: header. This is an issue because this is the kind of email that's generated by the get_maintainers.pl script in the linux kernel.
Tried this as well and get an error message from mailer@lists.sr.ht in reply:
The To header is required.
Searced around in the lists.sr.ht code and in some of the python dependencies but couldn't find anything which by default does this. RFC 5322 specifies the date and originator fields as the only required headers for email. Was this intentionally set for sourcehut?
Yes, this is a requirement specifically for sourcehut, but it would be better to also allow Cc.
For reference, made a patch for this: https://lists.sr.ht/~sircmpwn/sr.ht-dev/patches/10353.
Fixed with 9a66457c.