I've run my own mail server ever since I got something resembling broadband internet in 1996. Back then spam was non-existent, Sendmail was the emperor without clothes about to be dethroned and I hacked sendmail.cf without needing to look at the the bible [1].
I've never regretted running my own server, nor have I ever contemplated moving to a hosted solution. Spam is not a problem either, Spamassassin in combination with a greylist make for a nearly spam-free experience. The whole setup has been migrated from the original Pentium-66 via an aBit-BP6 (SMP for the masses [2], retired in 2009) to the current Intel SS-4200 (upgraded to a dual-core Pentium but still limited to 2GB). In practice a Raspberry Pi would be enough to run a viable mail server so even this rather anaemic setup does its job without breaking a sweat.
The whole setup consists of Debian (Sid) running Exim through a smarthost, feeding through Spamassassin + greylistd into Dovecot. Apart from some auto-manual intervention to cope with Microsoft/Google/... not coping with the greylisting and thus needing whitelisting it more or less just works. In other words, just go ahead and run your own server.
Initial setup took a few days of experimenting, that was back in the days of Sendmail. After that is ran fine for a while until spam starting becoming a problem. I eventually implemented a spam filter with Spamassasim with a nightly cron job to train it with spam which made it past the filter. After a few years I added greylisting to the mix which ended up complicating matters a bit due to some common mail hosts (Google and Microsoft being the biggest culprits) breaking the concept of greylisting by using different mail hosts for resend attempts. I made a script to add all SPF-allowed IP ranges for a domain to the whitelist which solved that problem.
Total time spent on the mail infrastructure over these 22 years is negligible, probably ~8 hours per year.
Not the OP, but I've been running my own email server since about the same time-frame (and it started life on a dual CPU Pentium 100Mhz box). Total time investment since circa 1998: estimated maybe 100-200 hours total (note, over an approximately 20 year span), and most of that was spent during the inevitable of reinstall new OS on current or newer box, then move config over portions of the process.
I've also always been on Postfix, which has always been way more secure than sendmail ever was at the time. And Postfix is also much easier to configure for the basic case of "send/receive email for a personal domain".
I've never regretted running my own server, nor have I ever contemplated moving to a hosted solution. Spam is not a problem either, Spamassassin in combination with a greylist make for a nearly spam-free experience. The whole setup has been migrated from the original Pentium-66 via an aBit-BP6 (SMP for the masses [2], retired in 2009) to the current Intel SS-4200 (upgraded to a dual-core Pentium but still limited to 2GB). In practice a Raspberry Pi would be enough to run a viable mail server so even this rather anaemic setup does its job without breaking a sweat.
The whole setup consists of Debian (Sid) running Exim through a smarthost, feeding through Spamassassin + greylistd into Dovecot. Apart from some auto-manual intervention to cope with Microsoft/Google/... not coping with the greylisting and thus needing whitelisting it more or less just works. In other words, just go ahead and run your own server.
[1] http://shop.oreilly.com/product/9780596510299.do
[2] https://en.wikipedia.org/wiki/ABIT_BP6
[3] http://ss4200.pbworks.com/w/page/5122751/FrontPage