Does the problem happen with all email accounts or just some? (microsoft servers such as live.com and hotmail.com notoriously delete and reject valid emails when others do not).<p>Besides spf, make sure that you comply with can-spam guidelines. Ensure that your DNS entries are correct and that the url that you are sending from @example.com resolves to the same ip address as that url example.com.  Here is some more info <a href="http://postmaster.msn.com/Guidelines.aspx" rel="nofollow">http://postmaster.msn.com/Guidelines.aspx</a> . I had to add sender ID to my dns to get hotmail to accept forwarded messages from my disposable email service <a href="http://whyspam.me" rel="nofollow">http://whyspam.me</a><p><a href="http://www.microsoft.com/mscorp/safety/technologies/senderid/resources.mspx#ESE" rel="nofollow">http://www.microsoft.com/mscorp/safety/technologies/senderid...</a><p>get back with some more info, and i'll help you troubleshoot, seeing as how email is my current specialty.