I'm having this problem with Stripe: When a user choses to pay an invoice by card (Stripe has one-time payments on), but the customer doesn't get the modal box to put in their card and instead the pages takes a couple of seconds and shows the error "There was a problem with your payment...." and...
I sent a message from our main CE Gmail account and it bounced saying the account had reached its sending limits. Looks like the looping had triggered a spam flag.
It's all working now :-)
This started happing all out of the blue this morning. When users try to submit a ticket or admin reply to ticket in CE, email notifications are not sent and the error shows the recipient email:
"Email to [email protected] was not sent due to an error in Email configuration. (addreplyticket)"