Regarding point #1, I have maintained Linux mail servers both for large shops as a professional sysadmin as well as for myself and small organizations, and each has been a very different experience.
In the large environment, mail server maintenance does take a disproportionate amount of time. But that's because the environment is so complicated: there are several layers of servers, mail is stored on NFS so there are weird locking issues, LDAP is used for user accounts, etc. There are some very bad failure semantics and if we're not careful, we start bouncing mail.
My small setups use exactly the same software (Debian, postfix, dovecot, spamassassin) but the environments are much simpler: one server, no NFS, no LDAP. I use a VPS so I don't have to worry about hardware. Backups are an off-site rsync in cron. Failures rarely happen but when they do the semantics are much nicer: temporary failures so the mail is resent later. My VPS host failed for the first time in 5 years recently, so I couldn't get mail for a few hours, but I didn't lose any mail and didn't have to spend any time on recovery.
I also run other stuff on my VPS, so the monthly cost and recurring maintenance overhead (security updates/backups) is amortized. Adding mail as another service doesn't change these costs.
In the large environment, mail server maintenance does take a disproportionate amount of time. But that's because the environment is so complicated: there are several layers of servers, mail is stored on NFS so there are weird locking issues, LDAP is used for user accounts, etc. There are some very bad failure semantics and if we're not careful, we start bouncing mail.
My small setups use exactly the same software (Debian, postfix, dovecot, spamassassin) but the environments are much simpler: one server, no NFS, no LDAP. I use a VPS so I don't have to worry about hardware. Backups are an off-site rsync in cron. Failures rarely happen but when they do the semantics are much nicer: temporary failures so the mail is resent later. My VPS host failed for the first time in 5 years recently, so I couldn't get mail for a few hours, but I didn't lose any mail and didn't have to spend any time on recovery.
I also run other stuff on my VPS, so the monthly cost and recurring maintenance overhead (security updates/backups) is amortized. Adding mail as another service doesn't change these costs.