RE Test email from Joomla! admin: Just tried it, email came through lightning fast...
I will compare my old version's db with current version's db and see if I can spot anything...
The images are the same because I didn't change anything. I only amended them in testing to try and get a result
I just tried again with the old version then upgraded to see effects, you are definitely correct about Joomla 3.6.0! and some change within
Joomla! 3.5.1 (Seblod 3.8.4) = RESULT (email sent)
Joomla! 3.6.0 (Seblod 3.8.4) = NO RESULT (email not sent)
Joomla! 3.6.0 (Seblod 3.9.0) = NO RESULT (email not sent)
don't search for the differences as it is not the cause, you need to figure out which setting is causing this. Usually the problem is in the To or To(fields), but your setting seems ok. Since Joomla 3.6 is performing strict checks on the email from, to etc fields and if something is missing or is not configured correctly it won't be sent. I would try changing fields one by one to see which one is causing the problem.