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by cesarb 3075 days ago
And you need these patches to fix what is IMO qmail's worst problem: backscatter. As far as I remember, when receiving an email with a forged return address to a non-existent mailbox, qmail first accepts the email, then sends a bounce message to the forged return address. Other MTAs (and patched qmail) reject the email directly in the SMTP session, preventing this issue.

I personally consider this backscatter issue a design bug in qmail.
2 comments
NoGravitas 3075 days ago
I worked at a web hosting company 1999-2005 that used qmail, and while there were many things wrong with qmail, due to it not being designed for the realities of email circa 2001, backscatter was by far the worst. We were processing significantly more backscatter than valid email, and to the best of my knowledge, the patches to address it didn't yet exist.

We certainly should have switched mail servers, but qmail was deeply ingrained in our home-grown hosting automation system, and it would have been a big deal to change.

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stevekemp 3075 days ago
That was definitely true, and it was the reason that I personally stopped using qmail in a previous (very long time ago now) job.

There were patches to fix the problem, along with offering useful features, but for whatever reason we went with exim (exim 3.x from Debian).

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