Customizing Email Template so it won't be flagged as spam by mail

Hi, I'm sending mail via SMTP ( it all goes fine ), checked my IP @ http://mxtoolbox.com , its clean, so according to WHMCS documentation,

If it is suspected that the wording of an email being sent by WHMCS may be triggering a filter, try customizing you email templates so they do not appear exactly like every other WHMCS installations emails.

This should be the problem.

Has anyone else experienced this ? And if so, which part of the email template did you edit ? ( The wordings, or css/header/footer ? )

Thanks in advanced !

Which emails are being marked as spam? Do you have correct Reverse DNS for your mail IP?

Hi, I solved it, I didn;t have proper PTR records , my bad!