Resolved (I think) but I'm confused
Thanks for the advice but the two separate email triggers are for two separate purposes - One is customer email and the other is an internal admin notification. I have also gone through and checked the addresses and all the code in the email. I even have tried a simple plain email but nothing would send.
After several hours spent trying to resolve this, I have discovered that for some very strange reason the issue is with the subject line. The variable I use here gives the subject line of "Reservation Request":
$Email->Subject = "".($WAGLOBAL_Availability_Email_Admin_Subject) ."";
However, I tried changing it to something else such as "Email Server Test" and it worked! In conclusion, for some odd reason it will not work with the subject line of "Reservation Request" and so in the end I have settled for a subject line of "New Reservation Request" and the email works and is received.
My only assumption is that something (perhaps my new hosting provider's platform??) is blocking emails with this subject line?? I am going to contact them now to see what they say.