Big question is: who’s storing the email, you or them? Your mail clients handle POP3 and IMAP as well as SMIME and GPG so the server doesn’t have to have any special features itself.
Since you want something your wife can manage, stay away from the forwarders. Whatever you choose, check Spamhaus and SURBL to see if the provider has a history of getting on their lists.
Make sure you select one that can stay in business providing email service, so you don’t have to worry about the company collapsing/being bought out/pushing ads/selling PII/bundling mail with some more lucrative service.