Getting Recipient address rejected: broadband/ returned deny

Hello,

We are on the SmartMail build 100.0.7242.24590. The mail server is only used for relaying emails from our application. So we have the Protocol Settings SMPT In set to Allow Relay: Nobody. Allow relay for authenticated users and Enable domain's SMTP auth setting for local deliveries are checked. On the domain, we have it set to Require SMTP Authentication is checked. The logs show:

554 5.7.1 : Recipient address rejected: broadband/ returned deny: my-domain (IP address) looks like a consumer broadband machine

The email was trying to be sent to a user at pobox.com. So to troubleshoot further, I set up an email account at pobox.com also. I test my email and it went through.

So I'm not sure if this error is with our server or the recipient's email account. Any help in pointing me in the right directions would be greatly appreciated.

Thanks,
Marc

Gabriele Maoret - SERSIS Replied

5/11/2020 at 8:26 AM

That message means that you are sending mail directly using you consumer Internet connection IP address (probably a dynamic one...).

This is deprecated and it's normal that many antispam systems block your email.

You need a static IP Public Address assigned to your mail server by an authority (or a provider) and you must configure it to be used as a mail server.

You then need to configure:

PTR entry (reverse DNS) - this one probably need to be made by your internet provider
SPF record in your public mail domain DNS
correct IP nat and security so your mail have your authorized ip in their envelope
other adavanced settings if you want to have more security (SSL, DMARC, etc...)

Gabriele Maoret - Head of SysAdmins at SERSIS Currently manages 6 SmarterMail installations (1 in the cloud for SERSIS which provides services to a few hundred third-party email domains + 5 on-premise for customers who prefer to have their mail server in-house)

Marc Rohrer Replied

5/11/2020 at 9:58 AM

Hi Gabriele,

The email server is on an Azure VM with static IP. We have the reverse DNS and SPF record. The email server and application are both on the same server using 127.0.0.1.

It's interesting that you mentioned "sending mail directly using you consumer Internet connection IP address". Because the email is being sent from the same location and I tested the two different accounts at pobox.com. The one that was having the issue and the new one I just created. The new one got through. Since the email being generated from the same location and using the same email server, would "using consumer internet connection" come into play?

Thanks,
Marc

Gabriele Maoret - SERSIS Replied

5/11/2020 at 11:35 PM

Maybe there's a problem with the IP configuration or some other issue... It's difficult to look at it without further details and/or the access to the machine.

I can make some hypotheses, but then you have to check carefully. Some of the possibilities are these:

your static IP is in some blacklist
your PTR record is not configured correctly
for some configuration error the headers of your email report incorrect IPs

There may be other problems, but these are the first that come to my mind, and perhaps the easiest to check

It could also be that the antispam filter at pobox.com is too aggressive and reports false positives...

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