On Thu, Jun 11, 2020 at 05:02:03PM +0800, Plutocrat wrote:
On 11/06/2020 16.26, Marc Roos wrote:
I know it is not dovecot who should fix this. But anyone using dovecot is using an MTA, and receiving spam ;) I know how to look at email headers. Spf and dkim is not solving anything here.
You can configure this sort of thing in postfix, exim etc. The part of the mail system to do with RECEIVING emails. Not really a dovecot function.
Look at greylisting as an option. That's basically delaying email from unknown senders.
I use greylisting with my postfix. On Debian and Devuan th package is called 'postgrey'.
What it does is, opon receiving mail from a new sender, reply with a protocol code that indicates "service temporarily unavailable; try again later". Real email senders will try again later. Most, but not all, spammers don't bother.
It does mean that the email services of some legitimate senders will take that protocol code and tell the user that the email was undeliverable. (so the senders tell me) But those services still do try later, and I do get the message.
Of course you can still whitelist, and this spamfighting won't happen for those sites.
-- hendrik
Also blocklists Also consider setting up rules in spamassassin / rspamd