On Sat, Oct 14, 2023 at 03:06:11PM +0200, Sagar Acharya wrote: > How do I reject all emails with attachments by using an opensmtpd filter?
You need to parse the content of the emails using the data-line filter event. You'll probably want to check the headers for Mime-Version: and Content-Type:. If the message is indeed Mime encoded then look in the message body for the Content-Type: header again, and decide whether to pass it or reject it. (You might want to pass some attachments such as plain text or text/html, and reject all others.) > At what step do I set the filter? rcpt-to, data, or commit step? You will need to parse several events, probably at least: link-connect link-disconnect data-line and maybe others. > Any tutorials are appreciated. If you want a general tutorial about writing filters in C, you could look at: https://research.exoticsilicon.com/articles/mail_filters Some of the content is applicable to other programming languages too, but the tutorial is based on programming in C.
