We are trying to troubleshoot email delivery. We have latest version of Subscribe2 and Email Log plugin confirms all emails are sent. Unfortunately, some Registered Subscribers fail to receive them.
Our host provider (we are on a Managed VPS plan) has advised this:
"We are not blocking any of the emails that you send through WordPress; however, if you are sending them through WordPress they are most likely being sent via php mail() function. Most receiving mail servers will either reject email sent as php mail() or place them in spam due to the lack of email headers. The below URL provides more details on adding header information to your php mail script.
Any thoughts on their response and/or solutions?
Bu the way, no problem with emails for public subscribers.