I've been migrating a relatively simple PHP site to GoDaddy from a host that allowed SMTP connections to smtp.office365.com. I just gave up trying to get that to work from GoDaddy as I believe they insist you use their email servers, e.g. n3plcpnl0109.prod.ams3.secureserver.net
The checkout function sends two emails. One to the customer and another to the vendor. The first one worked a treat after switching to GoDaddy's SMTP server. But the second email never arrived.
I've spent *hours* tracking this down and it boils down to this line:
$mail->Subject = "Order Received";
I implemented a test mail page to isolate this and indeed. If one sends an email with that subject line, it is never received. If you change it to (say) "Order #1734 received", it works.
What is going on??? I can only think that some filtering is going on somewhere. I changed the destination email address directly to my Google account just to check it wasn't going into spam. It's not. It's never received.
Thanks for posting in our forums! All GoDaddy servers that use our outgoing mail servers check email for spam. If the email is coming from the server, which it was in your post, it is being scanned. Each email is sent through an external relay server, that is specified in the MX record, that MX record is then checked with an SPF record (txt) for allowed outgoing mail servers. Please contact our hosting team to verify that your email is not being blocked for previous spam content and is now being flagged. Our hosting team can be directly reached by dialing 480-463-8824.