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Comment by vilda | Hacker News Reader

Please please don't use greylisting. It's not cool. There are too many broken mail servers around and you'll loose emails. I was unfortunate enough that I had to use mail server with greylisting enabled. As a result I regularly lost booking confirmations.

Spammers know greylisting. Workaround is cheap for them. That's why you are receiving some spams twice.

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Not in my experience. I'm using greylistd with Exim and a custom config which uses geolocation to do greylisting by subnet country code. I've only needed to whitelist a handful of broken MTAs which don't retry.

My spammers clearly haven't caught on yet...

      zgrep grey /var/log/exim4/rejectlog* | rev | cut -c 2-3 | rev | sort | uniq -c | sort -rn | head
      8 CA
      7 IT
      5 ES
      4 BR
      4 AR
      2 TR
      2 RO
      2 IR
      2 EC
      1 PT

What do you mean too many? there are so few legit servers that will not resend an email and you can whitelist those.

I silently lost email from my accountants because of some sender verification misconfiguration. Silently dropping email seems too risky to me. Checking the greylist and then marking the email accordingly sounds like a good compromise.

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