On 2023/10/14 15:06:11 +0200, Sagar Acharya <sagaracha...@tutanota.com> wrote:
> How do I reject all emails with attachments by using an opensmtpd filter?
I never used it, but from the look of it you could try mimedefang via
the filter-mimedefang package. It's available on OpenBSD, but being
written in perl I assume it would work everywhere.
https://mimedefang.org/download/
> At what step do I set the filter? rcpt-to, data, or commit step?
>
> Any tutorials are appreciated.
Other than the link posted by Crystal, I don't think there are any
tutorials on how to write an OpenSMTPD filter. However, the protocol
is described in smtpd-filters(7) [0], and you can take a look at
existing implementations, like filter-rspamd[1] (which is written in
Go) or at a library like libopensmtpd[2] or OpenSMTPd-Filter[3] which
should simplify the task of writing a filter.
[0]: https://man.openbsd.org/smtpd-filters.7
[1]: https://github.com/poolpOrg/filter-rspamd
[2]: http://imperialat.at/dev/libopensmtpd/
[3]: https://metacpan.org/dist/OpenSMTPd-Filter
