sendmail logs "possible SMTP attack: command=HELO/EHLO, count=3"

Solution Verified - Updated -

Issue

When trying to send multiple mails simultaneously, it fails to send all of them, logging the following error on the /var/log/maillog. It seems that it has an association with sendmail security. How can I ease this restriction?

possible SMTP attack: command=HELO/EHLO, count=3

Environment

  • Red Hat Enterprise Linux
  • sendmail

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