Dear all,

our problem is that certain MX/DNS resolutions are not working properly for external users trying to send us
email.

For example, mail users at yahoo.com are getting rejected when trying to send an email to us at "123@example.com".
This mail is rejected as the user "123@WWW.example.com" as
not a valid email address.
It appears that YAHOO is resolving our CNAME and although
people are trying to send to @example.com it is being re-
solved to @WWW.example.com which our mail server rejects.

Amazingly mails for example from hotmail.com, gmail.com or
mail.com are working!

Would be great to find here a solution and/or an expla-
nation for this instance.

THX, Rainer

Do you know where your reverse DNS points?

@billymayday:
1. there is a typo: mail address for external users is
123@mail.example.com
2. Reverse DNS points to: WWW

Does your comment mean to set the PTR to 'mail'?

It was just a guess, but would seem like a likely cause. Looks like yahoo is stipping the domain and appending the reverse DNS result.

You do mean web users of yahoo rather than some other client connecting via yahoo don't you?


Rgds

What's about to have two A records with the same IP i.e.

mail IN A 1.2.3.4
WWW IN A 1.2.3.4

and delete the CNAME entry?

Rainer

Yes, create two A records. CNAMEs are not allowed in MX records.