501 Domain must resolve


Have a problem with email, where if I do not route our exchange mail through our ISP's smart host then a certain domain wont allow our email (genzone.net).

I simply cannot route the mail through the smart host though, because we get loads of bouce backs again because its sees to much of our mail as spam due a CMAE Filter, BTW my ISP is DEMON, and this isn't happening to just me.

I cannot see my current mx record though.

Is the reason why my messages are being blocked by genzone.net because I haven't got an MX Record?

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Simon Butler (Sembee)Connect With a Mentor ConsultantCommented:
You don't need an MX record.
However you must have a PTR record set.
You will also need a valid host name that points to your server and have that host name set as the FQDN.

Call Demon Internet and get them to set a PTR. Then wait. They only update once a day (at 5pm) so you will have to wait until they do that.

If you are sending email it would also help if the SPF record on the domain was setup as well.


Please see below link for detailed description: "Syntax error in parameters or arguments (e.g. invalid email address)"
xObIAAuthor Commented:
Thanks, although surely if this was an incorrect address or "Syntax error in parameters or arguments (e.g. invalid email address)" then the mail wouldn't route in any situation?
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what dose an internet message header say, from one of these e-mails?
Mohammed KhawajaManager - Infrastructure:  Information TechnologyCommented:
Check www.mxtoolbox.com and post the results.
Naushad shaikhIT Consultant - Messaging SupportCommented:
You are getting email bounce from those recipient  email domain which are configure for the revers lookup , these server are checking your PTR record  no matter you send email with your smarthost  or directly with your exchange server . you have to configure your PTR with you ISP end for your server ISP which you are using for public IP for your exchange server .till time reverse query will fail for your server (genzone.net). this issue will remain same.because your email header consist xyz@genzone.net what is public IP for this server and is name and IP matching
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