One can argue that everything transmitted on the Internet and wireless telecommunication links is a message of one sort or another.
Once email spam and computer virus problems started becoming prevalent in the early 1990s.
These critical Internet infrastructure systems had to be patched and the underlying protocols changed -or in some cases ignored- to deal with these issues.
Large telecommunication operators and internet service providers needed flexible, easily deployed and scaled messaging systems for quickly growing messaging services and cell phone networks (for examples see SMS and BlackBerry.)
Smaller operators and ISPs have generally relied on open-source software, like Sendmail, and in-house system administrators for maintenance.