A Simple Anti-Spam Technique That Works!

By admin, May 27, 2014 6:25 pm

Out of blue, after years of searching for the best way to prevent spammer from inside. I think I probably found the solution by extending Delay between Recipients to 5 seconds on Outgoing SMTP, which keeps the email password cracker away. :)

It’s really more a mind tactic than the actual technical solution, as the spammer will give up right away if they find your SMTP server is so slow sending out emails per second. I strongly suspect they have a set of standards, say if a SMTP server can’t deliver more than 10 email per second, then they won’t use it…after all, why bother to use a slow SMTP while they are plenty powerful ones out there.

In contrast, by using Grey Listing on incoming SMTP also greatly reduced the spam or email DDOS by a large percentage.

Just my 2 cents.

Update: Jan 16, 2018

Today client’s email server had a DDOS attack, one of the users got tens of thousands of email and this made the spooler almost crashed, hence CPU stays at 100%. Solution is to decrease the SMTP Delay from 5 seconds to 1 second, so the email server can quickly bounce back the email (of course, remove that user temporarily).

Lesson learned, Delay SMTP delivery may cause dearly at a specific occasion, so use it wisely according to the actual filed scenario.

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