Just a quick followup: After I added a second 512MB swap file on January 12th I haven't had an invoked-oom failure. I have had some high swap activity and will consider deleting the 512MB swap file and creating a 1024MB swap file. A search of an older /var/log/messages file shows that several processes were being killed by the oom manager, not just mysql. As performance isn't an issue I will change some of the mysql settings to reduce its memory footprint.

For a low volume site this basic linode server looks to be adequate to run my ClearOS 7 Home Essentials with Zarafa. If I needed more performance in a real work environment I would opt for the $20.00/month 2 core, 4GB RAM option.