I've been setting up a newsletter using Simplenews - it works well enough but only for plain text emails.
I've set up and installed MimeMail but when selected as the site-wide default [admin/config/system/mailsystem] no emails are sent through the site at all - contact forms don't deliver a message and test newsletters aren't sent, though they do both cause a positive message to be displayed above the content.
This page [admin/config/services/simplenews/settings] is all set up for HTML emails.
Previously I was able to send HTML emails from this exact site but I'm not sure what I could've changed. Is it server side or is my email blocking them for some reason?