Here are the downsides to outsourcing your email:
- Who will read your mail sitting on their server? - Who will give your mail sitting on their server to anyone waving some legal papers? - Who can kick you off their server without recourse, killing many years of investment into your email identity?
Here are the downsides to rolling your own email server:
- If an evil hacker invades your badly protected server, and uses it for gadzillions of spam, a nicer provider will turn off your outgoing email, a nastier one will null-route you no questions asked. That’s why you should start your career as an artisanal mailhoster on a VPS -- you can always rent another one. It gets nastier when a homelabber decides to do it from home. Hacker invades, Internet provider cancels your account for violation of TOS. You usually don’t have much choice when it comes to a new hardline provider, and it will take a while. - A big danger are the countless blacklists. It is very hard not to be on any. Some will blacklist whole net blocks if one IP in the block misbehaves. Some are plainly extortionist; they want money for removal. Frankly, they should be taken to court.