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Goofy errors prevent some mail recipients from getting my server's messages

Posted on 2011-10-25
Medium Priority
Last Modified: 2013-11-10
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[] said: 550 Access denied -
   Invalid HELO name (See RFC2821 (in reply to MAIL FROM command)

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<SOMEONE@kcaccess.com>: host mail.kconlineinc.com[] said: 554
   Confused? 05 (in reply to MAIL FROM command)

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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?

Question by:Daniel Wilson
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LVL 19

Assisted Solution

xterm earned 800 total points
ID: 37025713
The error about Reverse DNS not matching your SMTP banner shouldn't matter too much.  It just means that the value returned by "nslookup <your IP address>" does not match the name in the welcome banner string shown when you telnet to <your IP address> on port 25.  Nobody anywhere should deny email on this basis.

The commonality is the MAIL FROM: part of the error, which sounds like perhaps a malformed return address on your customer's part, not necessarily anything to do with Postfix misbehaving.  I would suggest setting up a 'tcpdump host" and have your customer mail the kconlineinc.com address again.  Probably the best bet would be to redirect it to a capture file which you could then step through with Wireshark, and find the MAIL FROM: line so you can see what she's putting in there.  I'll bet that will yield the answer you're looking for.
LVL 32

Author Comment

by:Daniel Wilson
ID: 37026009
setting up a 'tcpdump host"

How do I do that? Would that be in a config file somewhere?
LVL 19

Expert Comment

ID: 37026028
No, you will need to install the program tcpdump:

$> sudo apt-get install tcpdump

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LVL 21

Accepted Solution

Papertrip earned 1200 total points
ID: 37026037
As xterm said, if the receiver is rejecting mail because of a HELO/PTR mismatch, they are just doing it wrong and nothing you can do about it.

That being said, if possible you should make the HELO/A match the PTR if possible, if not you should at least make it a FQDN, not localhost.  I'm guessing your machine is still named localhost, and that myhostname isn't set in main.cf.

[root@broken ~]# telnet 25
Connected to
Escape character is '^]'.
220 localhost ESMTP Postfix (Ubuntu/GNU)
helo asdf.com
250 localhost

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From main.cf
# The myhostname parameter specifies the internet hostname of this
# mail system. The default is to use the fully-qualified domain name
# from gethostname(). $myhostname is used as a default value for many
# other configuration parameters.
#myhostname = host.domain.tld
#myhostname = virtual.domain.tld
LVL 32

Author Closing Comment

by:Daniel Wilson
ID: 37028344
Thanks to both of you for the help.  Setting myhostname seems to have solved the problem!

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