3+ hour delay to send out welcome email

We are trying to track down an interesting issue with the Membership plugin. When a new user registers, the WP username and password email goes out immediately.

However the Membership "welcome" email that is set to go out 0 days after registration doesn't go out until a few hours later. about 3.5 in today's case.

Is there anything I can check to see if it's sitting in a que somewhere? Or a cron job delay? I'm far from an expert, so any guidance on what to check would be awesome.

Thanks!
Ian