ID 437777 - [S] Flix email queue gets stuck after getting an error about an invalid email address

Problem summary

Flix email queue gets stuck after getting an error about an invalid email address

Customer reported version
flix_6.3.3_103

Customer reported platform

Steps to reproduce

1) Add a user with an invalid email to a group that has permission to a show.

2) Publish a sequence from that show.

Expected behaviour

All users who have permissions to the show should get a published email.

Actual behaviour
Only some people get an email. Flix starts emailing users one after the other, but after it reaches a person with an invalid email it gets stuck