I am running Postfix 2.7.0 on an Ubuntu virtual machine.
Mail has mostly been working, but one of my customers is getting mail bounced when she sends to certain recipients. She forwards the messages to a GMail account just fine ... and from there to the original recipient just fine.
I think that my Postfix server must be messing up the dialog with the intended recipients' servers a little and they're rejecting it ... but that GMail is more lenient. But I want my Postfix server to behave!
Here's one of the error messages:
mail.REDACTED.com[126.96.36.199] said: 550 Access denied -
Invalid HELO name (See RFC2821 188.8.131.52) (in reply to MAIL FROM command)
<SOMEONE@kcaccess.com>: host mail.kconlineinc.com[184.108.40.206] said: 554
Confused? 05 (in reply to MAIL FROM command)
I'm not finding any red flags when I use http://www.mxtoolbox.com/SuperTool.aspx?action=mx%3awilliamstonconsulting.com
Well, a warning is there:
Warning - Reverse DNS does not match SMTP Banner
Could that cause it?
If not, what should I check to get this working?