I list my troubles trying to get my email host (tsohost.com) to work with Plone. @dieter has been a great help trying to troubleshoot. I'm looking for a different option.
However, maybe the easiest thing is for me to move to another email host. so here is my question
What email hosts have people be able to get to work with Plone (not including localhost)?
I either use sendmail on the host itself or use the Gmail SMTP server.
Any mail server will work, provided your host can contact it.
Moving to another host will add more costs, but won't automatically fix the problem.
You are not unique in this regard, please be patient. There is also the option of hiring someone if time is of the essence.
We're using mailjet.com ... there you have logs and statistics of the delivery state. But its a payed service and you need to have access to your DNS in order to configure SPF and DKIM entries.