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I had this Warning with mxtoolbox. I know that it's not necessarily a big problem, but since we are having lots of issue with email delivery, I want to check everything.

I have a Exchange server 07 + Sonicwall.

My FQDN is for send/receive connectors. When I try : telnet 25 --> 220 MYSERVER.mydomain.local Microsoft ESMTP MAIL Service ready at Fri, 7 May 2010 10:34:36 -0400

I can change my SMTP Banner in the Sonicwall, but I don't know what to write, if there is a specific syntax or what can be the consequence if it doesn't work.

Thanks for your help.

edit: Here's the result for the SMTP test:

220 ESMTP SonicWALL (

Not an open relay.
0 seconds - Good on Connection time
0.296 seconds - Good on Transaction time OK - resolves to
Warning - Reverse DNS does not match SMTP Banner

Session Transcript:
250 [78 ms]
250 2.1.0 MAIL ok [62 ms]
550 5.7.1 Unable to relay for [78 ms]
QUIT 221 2.0.0 Bye [62 ms]

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up vote 3 down vote accepted

In the SMTP service of Exchange there is a special setting to override the hostname exposed by SMTP server during SMTP greeting. I think it is inthe same window of the smart host setting (sorry I don't have an exchange server at hand right now)

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+1 for the only one knowing what the OP talks about ;) – TomTom May 7 '10 at 16:16 ( is my Sonicwall) This is it ? – Bastien974 May 7 '10 at 20:13
Can someone confirm please ? – Bastien974 May 20 '10 at 15:06
Bastien974: correct, that is the window. Note that if yoi use the square brackets you override the DNS lookup. – lrosa May 21 '10 at 4:52
You mean the [] as it is already ? I doesn't override right now, if I click the checkbox it will ? – Bastien974 May 25 '10 at 13:35

You need to Type in the FQDN of your Domain MX Entry

Make follow on the Shell

nslookup set q=mx

And here we are you see the MX Host A-Record Name of your Domain This you need to use on your smtp banner.

Something simmaler to this<>

Hope this helps.

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The response you're getting via telnet is different that the one you're getting from MXToolbox, but I'm assuming you've setup your SonicWall as an SMTP relay for your Exchange Server.

You can set the banner to whatever you wish as long as it starts with 220. To have it match, just put "220 ready" in the SonicWall where you configure the banner (it may actually put the 220 in for you, I don't know, as I don't have any SonicWall experience).

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