I have been using email to send reservation requests from my website hosted on GoDaddy. This month it stopped working I hav enot changed anything on the website. I use Netobjscts Fusion to build my website and the PHP Mailer may be old but what has changed??
Sounds like it could be related to the mail server config...I had this issue a month or so ago as well (but I was only using the built in mail function). I did some adjusting of the headers because a friend mentioned that it's common for mail servers to block any outgoing mail if the email has content that could be considered spammy (like noreply@ addresses set as the sender). It would help if you included information on what protocol you are using to send the mail as well (SMTP, TLS, etc). Let me know if you tried this and it works!
Stumbled over this old post as having problems too ...
... did you have a url in the email msg body? do you have shared hosting plan?