XF 2.3 Has something hacked into my forum?

[knobby]

Tonight when logging in to my admin page I was faced with loads of server errors, the majority of which are emailing errors. I use Mailjet for email delivery, but very few emails are normally sent. Tonight I was faced with over a hundred failed emails. Below is a picture of part of the server log:


Is symfony mailer part of Xenforo (in which case my problem is with Mailjet), or is it some kind of malware which I need to get rid of?
Thanks

 

[knobby]

I also found this in the server error log:

 

[briansol]

on the surface, it doesn't look hackey... looks more like a network was down and caused the failures.
pull your access logs and others to be sure.

 

[Alvin63]

Looks like an email issue maybe - I had something like this once when I was going over my email quota - had to upgrade to a different email plan and switch to SMTP. Are you on SMTP? I didn't think I was sending that many either.