Carrying on talking about OpenNMS features, this time I’d like to introduce the service called Mail Transport Monitor, normally abbreviated to MTM. The aim of this service is to monitor the complete functioning of your mail system: sending and receiving e-mails. For this purpose we need an “external” email which should rapidly answer to our request with a so called “echo-reply”, to let us know that everything’s working. Instead of putting an automatic reply rule to your ”free” Gmail/Hotmail/Yahoo (etc..) account, it would be nice to have an automatic service that does this job automatically, without any configuration. These services exists and they’re public (anyone can use them) but unfortunately they’re not so reliable as expected (if you only think at how many emails per seconds they receive, maybe this delay is understandable)
Here you can look at the most famous Echo-Mailer (just a German page on Wikipedia, Google helps you). After many tries, here’s my suggestion: email@example.com and firstname.lastname@example.org are the best choices. If you send an email no more frequently than every 2 minutes, you will never have problems with them (since 6-7 months). Now we can have a look on how it’s the configured OpenNMS and this tricky MTM service.