Microsoft Exchange server cannot send emails to certain domains eg.AOL I get this error "5.5.0 smtp;550 DNS FAILURE" I asked my ISP to creating a PTR record in their DNS server which cannot be done because of an _ in the domain name. What can I do to fix this problem so that I can send emails to any domain?
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<mailserver.base_domain.com #5.5.0 smtp;550 REQUESTED ACTION NOT TAKEN: DNS FAILURE>