I've been getting this a lot recently:
Delay reason: SMTP error from remote mail server after RCPT TO::
host mx2.emailsrvr.com [18.104.22.168]: 450 4.1.1 :
Recipient address rejected: undeliverable address:
host mail.telltalegames.com[22.214.171.124] said:
553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1) (in reply to RCPT TO command)
(actual issue number deleted)
So, it looks like the Telltale email server is borked or something...?