I am with mail jet and it works well.
I followed these instructions (for mail gun)
The difficulty I had was not with the host, but the domain provider setting. This might be your issue.
The text it told me to copy and paste did not work with cheapname.com. From memory I had to use “@“ instead of “myforumname.com”
Within mailjet there is a test to see if you have put these settings in correct.
Depending on size of your community you might consider sendinblue they allow 300 free emails a day. My site was originally with them and was a bit easier to get setup. But as my site grew I shifted to mailjet,