Edited:
EDIT 1: Could be an outbound spam filter problem. 
I believe this is most probably not a problem with MXroute, but if anyone can help, it would be great.
Visitors that try to register on my WP website don’t get registration confirmation emails. I get an email notification that a visitor has registered - but visitor doesn’t get the email with a registration link. Hence - I get no email notification that the visitor has confirmed the registration.
Had a similar problem before - not with MXroute. It was solved after a few weeks - the hosting provider needed to consult the SpamExperts and somehow got it fixed. Explained in detail here:
This looks exactly like that, only now I’m using MXroute (which, so far, has been with no problems - any problems I had had, turned out to be related to my setup, or something else).
What confuses me is that it has been working - until it stopped. No changes to the setup. Sure, WordPress updates can make problems (that is my main culprit), but I am trying to eliminate possible causes.
Any help, or advice is more than welcome.
I am using Easy WP SMTP plugin for sending emails - any test emails are sent fine - along with all the WP notifications to my email.
Also, newsletter subscription confirmation emails are working.
Just registration confirmation emails aren’t working.
EDIT 2:
Is it possible for anyone from MXroute to check whether any outbound emails are blocked from the domains:
From what I could test - subscriber confirmation emails are not received by subscribers, while other emails work. Could it be an outbound spam filter?
Email used with most tests is zlivook from Gmail, as well as one from yahoo and another from Gmail.