Reasons email is bad
- Spam is rampant
- Running your own server is a major pain
- If you aren't on gmail, gmail assumes you're sending spam
- Everyone else is on gmail
- Attachment limits are obnoxious and arbitrary
- Nobody knows how to validate addresses
- Configuring TLS, SPF, DKIM, submission, etc. is confusing
- Random RBLs will blacklist you based on superstitions, and admins of other email servers will trust RBLs without question
- Many useful protocol features have been completely forgotten in the quest to eliminate all spam (retry, MX forwarding, etc.)
- Random things don't understand MIME encoding for some damn reason
- Many clients don't know how to handle HTML correctly and/or safely
Reasons email is good
- Technically it's decentralized
- You can self-host it for not a lot of money
- There's a wide array of interoperable clients that work without a lot of proprietary nonsense
- Message headers are very extensible and useful for all sorts of unexpected things
- MIME encoding can do some really useful stuff
- It's private by default
- It's federated by default
- Spam filters have gotten pretty good for the most part
- You can have your own domain name and move it between different providers rather than being tied to your ISP and/or Google
Reasons email is better than the things people try to replace it with
- You can keep control of your notifications via message filtering, etc.
- Message filtering can be incredibly flexible
- Pretty good search (especially in modern clients, with client-side caching)
- Threaded messages can provide better context for a conversation and also allow people to self-edit and take more time to think about what they're going to say
- Writing "bots" and email-based APIs in general is much, much easier
- Signatures can add a lot of personality and useful information
- A broad choice of clients that satisfy varying accessibility needs without randomly A/B testing your experience
All in all, email is pretty okay.
(That said, if you want to run your own setup, Mailgun makes things a lot easier. Not sponsored, I just like them.)