Glad I went through this exercise. My upgrade has run into a hitch. 
@julian One place the lay person can check is Talos Intelligence. My network engineer buddy w/Crisco certs up the arse reports that their paid stuff is the snizzle. I only use the freebies so cannot comment. I just checked community.nodebb.org and the email rep is reported as neutral. Ditto all my stuff. Which may just mean we're both too hole in the wall to have had much, if any, or our stuff captured in their honey pots. In any event, there's one place to check. I hear used by lots of corp types so maybe just enough to know that you're not on their naughty list. Talos has DDos measures in place, so don't everyone /. that at once. Heck, I'll just post a screenshot:
0ff126fc-b955-4294-bdfe-f22dbcb7552c-image.png
Maybe remedy the forward/reverse DNS but otherwise all good. Well, community.nodebb.org does not actually send email. So let's check Sendgrid while we're at it, eh? Surveying a few incoming from the Robot, I note they're all coming from same MX, at least to my mail servers:
e6d73cfc-ea3b-452c-a5d1-213a308b77f7-image.png
Looks just fine and dandy. 🙂
So what about their other thousands of MX's? Well, just enter sendgrid.net to check and then scroll and page away. Most all is either good or positive. Indeed, the only "poor" ratings I noted were from democrats.org. And in that instance, pretty much all of the several I checked were on the naughty list. For whatever that may be worth: Mainly, that modern days Presidential Erections seem to spawn the lion's share of miscreants crawling out of the woodwork, irrespective of party (cuz I have tons of GOP stuff in my server logs so let's not make this about party politics).
And for some levity, I could not find Gilda Radner's infamous skit online but here's the text:
Emily Litella: What’s all this fuss I’ve been hearing about the 1976 presidential erection? Now, I know they erected a monument for Mr. Lincoln and President Washington, but that’s because they’re DEAD! Hopefully, the 1976 President won’t be DEAD! So he won’t NEED an erection! If Americans are going to spend money to erect anything, why don’t we tear down those nasty slums and erect luxury high rises for poor people and senior citizens! Not for presidents who can afford to pay for their OWN erections!
Chevy Chase: Miss Litella --
Emily Litella: I can’t believe the way things are turning out in this country -- what?
Chevy Chase: I'm sorry. That’s election. The editorial was about the presidential election, not the presidential erection. Election.
Emily Litella: Oh, that’s very different.
Chevy Chase: Yes.
Emily Litella: Never mind.
Chevy Chase: And that's the news. Good night. Good night, and have a pleasant tomorrow.
For the youngsters in the crowd, if you've never seen this, prepare to literally bust a gut laughing your arse's off.
Or.... eh... Never mind... ✌
Update: Foregoing is meant to be informational and no sleight on Sendgrid. Could just as well be any provider. Because.... there's always a sub population of miscreants who will try to exploit the hard work of others for jollies, profit, etc.
