Hi,
first of all: Thanks for this great software!
I would like to suggest some improvements for the future develeopment. I have seen that there have already been some requests in this forum for multi-tenantcy, multi-customer, etc. and while doing some reseach if have found https://www.mailwizz.com/ . I think it is a fork of mailtrain.org - but I’am not shure.
What I like about this solution is, that I can manage all customes (subadmins) AND configure a individual SMTP-server for each customer under one web-gui.
I think a good base for there SMTP-functionallity is given now with
define(‘PHPMAILERTESTHOST’)
define(‘PHPMAILERBLASTHOST’)
but unfortunately I am not a developer (just can offer some translations 
)
I would like to know what others think about these points.
Thanks!
Regards