I have been setting up opensmtpd and had this running for a few weeks now. Initially I had the rdns and fcrdns filters set up, but I found I was losing email so took those off. I suspect it was more about the fcrdns filter than the rdns. The original configuration was:
filter "rdns" phase connect match !rdns disconnect "550 DNS error" filter "fcrdns" phase connect match !fcrdns disconnect "550 DNS error" To begin reintroducing the filters but without completely rejecting email I was looking at the rewrite action. I was thinking maybe this could rewrite the email subject by prefixing with [Suspicious] or something like that so I could understand which filter is affecting which income email. But the manual says that with this action The command parameter is rewritten.. So does rewrite just affect a specifically tested value, e.g. if Id tested for a particular RCPT TO: value then it would rewrite this value? Or is there a regex possible to target the Subject: header? Or just another way of achieving this soft application of filtering to understand what its effect is before the more harsh disconnection format is used. Many thanks for any help on this, David.
