I've been self-hosting my email for over 10 years now (I'm going to link a bunch of my old comments on old email HN threads). I have fallen back to using Amazon's SES to send because all of Digital Ocean's IP blocks suddenly got marked as bad and I don't have enough volume to improve a new IP reputation - https://news.ycombinator.com/item?id=39891262, https://news.ycombinator.com/item?id=38471262
But as others here have suggested greylisting is extremely helpful in this space as legitimate servers should always retry. Well only my power company is the exception and they will fall back to sending paper bills, but even Gmail falls foul for them. It's also one big reason I'm not worried about up to a week downtime. But I have two email servers, a receiving and a storage server, the receiving is cattle and I car re-deploy in minutes if needed. - https://news.ycombinator.com/item?id=38512732
On greylisting I would say using https://github.com/stevejenkins/postwhite (even if it's very old and not actively maintained) has proven very important for the annoying 2FA emails, I strongly contend that email isn't suitable for this use case but that's another conversation)
I missed an incoming message (fortunately an unimportant one) from Amazon SES recently, since its 54.240.27.30 address was listed by bl.spamcop.net: Amazon kept trying different addresses while running into greylisting, until it tried that address and was rejected. Possibly it is less of an issue when sending between large providers (e.g., Amazon to Gmail), but apparently still not a perfect solution to ensure message delivery.
Sure but it really highlights that even big providers get black balled at seemingly random. I've had an email from a Microsoft email address come up in a spam list before. No one is safe.
And use it only for important things that won't be delivered if you don't send them from Google.
Receive only (e.g. account signup)? Use your own account. Not important anyway? Use your own account. Your recipient needs the email more than you? Use your own account. None of the above? Use a mainstream provider for that email only.
But this is why I'm using Amazon's SES for sending my very low volume emails now. It's never been blocked, if they ever start causing me grief I can switch to a new email relay service in a matter of minutes if necessary.
I use Gmail as a free spam harvester to train my own spam filter - https://news.ycombinator.com/item?id=38843288.
But as others here have suggested greylisting is extremely helpful in this space as legitimate servers should always retry. Well only my power company is the exception and they will fall back to sending paper bills, but even Gmail falls foul for them. It's also one big reason I'm not worried about up to a week downtime. But I have two email servers, a receiving and a storage server, the receiving is cattle and I car re-deploy in minutes if needed. - https://news.ycombinator.com/item?id=38512732
On greylisting I would say using https://github.com/stevejenkins/postwhite (even if it's very old and not actively maintained) has proven very important for the annoying 2FA emails, I strongly contend that email isn't suitable for this use case but that's another conversation)