[SOLVED] SMTP relay issues

[msnyder.cf]

I am having trouble with using PHPmailer-FE_v4.0.6/PHPmailer_v5.1 PHP libraries (by Worxware) when posting form data from an internal web server to an email address on the Zimbra mail server version 6.0.5 NE. The php script works with the Zimbra SMTP server when sending to an external email address but when sending to an email address that exists on the Zimbra server the script states that the email address is invalid.

Example: internal@mydomain.com will reject with invalid email address while internal@yahoo.com will email properly.

Thank you!

The issue was related to DNS. Solved with corrected DNS.