Mobile messaging growth will shift over the next 18 months with the transition of enterprise mobile e-mail to mobile e-mail on mass-market consumer phones, consulting firm Frost & Sullivan is predicting. As a result, global mobile e-mail usage is expected to grow 24% annually over the next four years, with particularly robust growth after 2008 due to increased consumer e-mail adoption.

Mobile open source software company Funambol and consulting firm Frost & Sullivan announced those findings today in a new report, “Open Source Push E-mail and PIM for the Consumer Market,” which focuses on consumer mobile e-mail. The report paints a positive picture of the service as a strong revenue source for wireless operators in the near future, in contrast to short message service and multimedia messaging service, whose revenues are expected to plateau, at 1% growth in the same four-year period.

“Mobile e-mail will become much more popular with all wireless subscribers,” said J. Gerry Purdy, co-author of the report, in a prepared statement. “Consumer e-mail will join enterprise e-mail as standard on mobile devices in coming years. Mobile e-mail that leverages open source and standards has the best chance for rapid adoption.”

The report also looks at how an open source, standards-based consumer push e-mail service could further benefit wireless operators.