I can't explain why this would be a thing, but it seems to be a thing: Every time we renew our certs, we start getting mail bounced by outlook/hotmai/msn, usually for a day or so. If we fill out the "please stop rejecting our mail" form, we eventually get a thing saying we're "not eligible" for that.
msn-com.olc.protection.outlook.com[188.8.131.52] said: 550 5.7.1 Unfortunately, messages from [redacted] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [DB3EUR04FT010.eop-eur04.prod.protection.outlook.com] (in reply to MAIL FROM command)
It doesn't seem that we actually stay on the block list for any length of time, maybe a day or two. And once or twice would be coincidence, but I think this has happened about every 2-3 months for as long as I've been using LE, it just took me a long time to start noticing the pattern.
I can't immediately figure out why, or what about any part of this would be related, but it seems like a heck of a coincidence unless the outlook spam protection is somehow picking this up and acting on the information that the cert is new or something?!?