Emails Blocked by AT&T

Hello,

Are our Email server emails being blocked because we are using an IP address rather than our domain?

We've recently fired up our new Exchange server.  Our emails are being blocked, cannot be received, by email boxes supported by AT&T.  I have sent in an unblock request.

Thanks,
~AJ
ajthomas12Asked:
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Dr. KlahnConnect With a Mentor Principal Software EngineerCommented:
Are our Email server emails being blocked because we are using an IP address rather than our domain?

Very possible.  Sender validation tools such as SPF, DKIM and DMARC can't be used to validate incoming email when only an IP address is provided.  The FQDN of the sender MTA should always appear in the HELO/EHLO exchange.

Many receiving MTAs will deny incoming mail from senders with only an IP address in the HELO/EHLO.  This is logical practice because (at least on my own system) any incoming email where the MTA did not identify itself properly always turns out to be spam.
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jmac44Commented:
Are you using AT&T Webmail?  Why are you using an ip address instead of domain name? That maybe why your being blocked. Go to mxtoolbox.com and run an mxlookup on your domain then click on find problems. Then reply back with the results.
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timgreen7077Exchange EngineerCommented:
First question is was the emails going out successfully before and is ATT your ISP?
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ajthomas12Author Commented:
Hello,  Sorry for the delay in responding to you all.

AT&T responded with this: "we have determined that reverse DNS is not setup correctly.  We advise you to set up a pointer (PTR) for reverse DNS so that it reflects your company's name, domain name, or another name that indicates the significance of your server."

I did some more research based on Dr. Klahn's response.  I ran Get-SendConnector | fl and saw that my fqdn was blank.  I set it by opening the Exchange Admin Center and going to mail flow -> send connectors -> clicked on edit pen -> scoping -> scroll to bottom -> FQDN:  here I entered our mail.domain.com and saved.  

This must of been overlooked somehow when we setup our exchange server.  Now I am wondering if this essentially satisfies what AT&T said our issues were or is there more that I need to do?  or is this another question for another thread?

Thanks,
~AJ
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Dr. KlahnPrincipal Software EngineerCommented:
Now I am wondering if this essentially satisfies what AT&T said our issues were or is there more that I need to do?

Only way to find out is to wait a few days and see if the problem disappears.

AT&T responded with this: "we have determined that reverse DNS is not setup correctly.  We advise you to set up a pointer (PTR) for reverse DNS so that it reflects your company's name, domain name, or another name that indicates the significance of your server."

rDNS setup normally is done by the owner of the CIDR block.  In most cases that would be the ISP who provides your IP address, unless you do own your CIDR block.
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jmac44Commented:
Who's your ISP. Their router should have a reverse lookup entry for your email server's FQDN. If they won't or can't then at the very least you need set one up in the DNS of whoever your using an Internet domain registrar (GoDaddy) and your internal dns must be up to standards.
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ajthomas12Author Commented:
Hello,

As far as I can tell the problem has been resolved.

Not sure if the solution was putting in the FQDN or that AT&T unblocked us.  I will update if I receive any more information.

Thanks for your help.
~AJ
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