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Mail Relay Testing

For mail hubs that found themselves a victim of spammers you can check if the relaying is accidentally enabled using MAPS Transport Security Initiative. For testing see Is my mailer vulnerable   For fixing information How can I fix the problem. You need to keep your MTA up-to-date. Holes in both sendmail (upgrade to v. 8.12.3 or later is recommended) and IMAP can be used to get root access -- see Relaying of Spam Email through Victim Sites . For sendmail 8.9 some discussion is in Using check_ in sendmail 8.9. For 8.8 in Anti-Spam Provisions in Sendmail 8.8.

Bridge wrote:
> Want to get some detail adive on how to test the that the sendmail daemon running on the is relay disabled? I understand that sendmail  8.9 disabled relay by default, is there a way to test it? Please give some detail. I also would like to have some details on how to prevent  sendmail from spam.

Start a shell, then:

$ telnet your_mail_server_name 25
MAIL FROM: user1@domain1
RCPT TO: user2@domain2

If your mail server has been configured properly, it will say something
about being unable to relay email.



The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D

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Last modified: March 12, 2019