OK...so I've been running a number of WordPress websites for a long time...recently decided to move everything to DreamHost so I could retire my own servers that I'd been running on forever.
I've always used WP-Mail-SMTP and Visual Forms Builder for my WP websites...never had any issue. So naturally those plugins were in my WP sites when I moved them to DH.
However, I noticed that sometimes an entry would be made by a user on the contact form that wouldn't show up in the Inbox (also using DH-hosted email for all my websites now).
All my VFB contact forms were set to use the user-provided email address as the reply-to - so that the people who receive those emails can just hit the Reply button, and respond to the actual user. What was happening was that if the user-provided email was on Gmail or Yahoo, for example, the contact form message would just poof disappear. It wouldn't get to the inbox, and it wouldn't get caught in a spam filter (DH or otherwise), and DH tech support says they wouldn't even see anything in the logs. If I switched the reply-to feature off, and just used the same DH-hosted email address that the form was getting sent to as the reply-to, all messages go through fine...but it's not easy for the receiving users to use, as now they can't just hit the Reply button and go...they have to copy/paste the user-provided email address (which is surprisingly difficult for many people to grasp).
I discovered that DH didn't automatically set up SPF records for my domains, which I found surprising...assumed their installerbots would do that automatically when you set up their email. Having fixed that, and verified that the DKIM is automagically set up by DH, I have no other ideas of what to look at.
DH tech support says that VFB is "doing it wrong" - such that they're not doing the reply-to bit correctly, and instead are making it look like a spoofed From address. Which I don't think is correct, because frankly VFB is so wildly popular and I can't find any indication of any such widespread issues - and I had no issues before moving to DH in the first place. I've verified the same type of behavior with a different contact form plugin too...so whatever it is that's happening, it almost certainly isn't specific to VFB.
I need help. Can anyone shed any light on what's happening here?