imapsync - Console-based utility for migrating IMAP mailboxes.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Gmvault - Backup the emails in your Gmail account.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Cryoserver - Cryoserver is an all-in-one email archiving solution that empowers you to preserve your email in a tamper-evident archive, making you transform your data into a useful archive for everyday use.
Prometheus - An open-source systems monitoring and alerting toolkit.