Question

550 5.7.1 Helo command rejected: Host not found

Asked by: LanMan6401

A user was trying to email us, they received this error.  This user has emailed in the past and has been able to email us after getting this error.  It happened on two separate occasions about two days apart.  I'm trying to determine what the error exactly is.

The receiving email server has a good DNS report, spf, reverse DNS, etc.

I see no log of either email in our spam software, the user had to send me this returned email error, it looks like we never received it to even reject it.

The message that you sent was undeliverable to the following: 
	user@domain.com (550 5.7.1 <domain.com>: Helo command rejected: Host not found) 
Possibly truncated original message follows:

                                  
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Asked On
2009-11-05 at 14:57:29ID24876433
Tags

550 5.7.1 helo rejected host

Topics

Email Servers

,

Exchange Email Server

,

Simple Mail Transfer Protocol (SMTP)

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Answers

 

by: alanhardistyPosted on 2009-11-05 at 15:28:01ID: 25755251

Can you divulge their domain name please - I can then check their domain on DNS and give you the reason.

Alternatively, please see these previous EE questions:

http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_21819179.html

http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_21387936.html

 

by: alanhardistyPosted on 2009-11-05 at 16:13:31ID: 25755565

Very simply - there are no MX records setup for the sending domain.  This is a problem at their end and they need to correct it.

Check this out yourself at www.mxtoolbox.com

 

by: LanMan6401Posted on 2009-11-05 at 16:45:26ID: 31650790

Thanks!

 

by: alanhardistyPosted on 2009-11-05 at 16:46:20ID: 25755767

Sorry - incorrect info - missed part of their domain name when copying / pasting.

Their problems are:

MX records do not match Reverse DNS records
Mailserver Greeting domain names do not exist
Not essential, but no SPF record.

 

by: alanhardistyPosted on 2009-11-05 at 16:50:05ID: 25755785

So it looks like your anti-spam software is checking their HELO name and finding it does not exist and rejecting them.

Have you upgraded / changed your anti-spam software lately?

 

by: LanMan6401Posted on 2009-11-05 at 16:59:19ID: 25755828

Yes, but a user is white listed once we send out to them.  The user account had sent email before and after the initial email blocks, with no log of being blocked in the spam software I use, Vamsoft's ORF.

I think I know what it is.  Zoneedit is the DNS host I use for this domain.  A few times this past year they have blocked email before we ever get it.  I'm willing to bet they blocked it before we received it.  I have no means of seeing a log from zoneedit, which is kinda frustrating.  I've been moving my DNS hosting to nettica.com.  They also block some email but provide a whitelist and log, just in case.

Thanks again for your help, Alan.

 

by: alanhardistyPosted on 2009-11-05 at 17:50:57ID: 25756053

No problems - sorry for the initial confusion over the domain.

I too use Vamsoft - great product isn't it?

 

by: LanMan6401Posted on 2009-11-05 at 18:06:39ID: 25756099

I absolutely love it and recommend it to everyone.  Easy to use, inexpensive and works great!  I've used it for the past six years (I think I've had it that long?) and they continue to add features.  The honeypot was brilliant.

20120131-EE-VQP-002

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