I'm trying various options for bounce processing, because mail seems to be flagged as Spam too often. My hosting provider (Siteground) is saying that SMTP is better than the PHP mail() route, but with SMTP the VERP return path isn't in the mail, so I don't get any bounce messages.
CiviMail works fine with the mail() option but no good with SMTP. The envelope return path is just the same as the From field. Nothing changed between the tests except for SMTP/mail(). Mail sent to individual users without CiviMail work fine in both option (but of course don't have a return path).
I'm aware of Siteground Email - How to configure?, which is likely to affect me if I solve this one!
I am also exploring other mail providers (SparkPost in particular), but I'd prefer everything in the same place and SparkPost is giving problems with too much being marked as Spam, but that is for a different post.
CiviCRM 4.7.27, WordPress 4.9.5 hosted at Siteground.