I was a Runbox customer for several years and recently switched to Mailbox and never looked back. Runbox is nice, but I had enough of reliability issues, and a few emails got lost.
5 karma · joined September 3, 2013
If I were you, I would use free monitoring services like uptimerobot. There are some other options available. Typically these services provide some basic functionality for free, it would be enough for a small enterprise.
On AWS it is quite easy to create your own external probes for a reasonable price. However, it would require some basic programming skills.