1

Suppose there is an instance of Sendmail 8.14.4 which handles incoming and outgoing email messages for domains a.com and b.com.

Now, what I'd like to achieve is the following: If Sendmail sends a message with a FROM of the form user@a.com, it should use mx.a.com as HELO name, and if it sends a message with a FROM of the form user@b.com, it should use mx.b.com as HELO name, i.e. I'd like to generate the HELO name for every outgoing message dynamically according to the envelope-from (SMTP MAIL FROM) or the From: Header, respectively.

Is this possible? Currently, I have configured the HELO name for all messages to be mx.a.com (using confDOMAIN_NAME or confHELO_NAME, respectively).

Binarus
  • 612

1 Answers1

2

Don't do it.

  1. It's completely normal for the HELO name to be different from the sender domain. Nobody will expect those to match.

  2. I've heard of a case where someone managed to configure his mail server in this way. Result was that he got himself blacklisted over the frequently changing HELO name.

  3. Some MXes will check your HELO name against your PTR. Although this practise is problematic and I recommend against it, you may still want to make your PTR match the HELO name to avoid trouble with such configurations. This, however, means that you can't change the HELO name on a per-message basis.

erebus
  • 156