Clearly there's a risk with running your own mail server (if it breaks for example) so it's better to have two, but Pis are not exactly expensive or costly to run. Plus there's the PITA for having to set up DNS for the mail exchanger and you need a fixed IP but none of these things are insurmountable.
There's a particularly interesting one designed by some former CERN people called Proton Mail (can't imagine how they came up with that) that's also open source - and secure end-to-end which may be worth a look. Of course, there are a number of other options, so far be it from me to lecture Daniel!
* It's hit DistroWatch now, so I hope people will send it some love and get it on the main page.