From the ebase Admin Manual:
"NOTE: If a problem is encountered that that the ebase mail function cannot
handle, both SMTPit and POP3it will give an error message that says,
“Developers Password Does Not Match”. This is a “generic” message that simply
means there’s an unknown problem. If you get this message, it typically indicates
that something has gone wrong with the plugins. Quitting FileMaker Pro and
ebase, then re-opening it resets these plugins so that you can continue to
troubleshoot the problems.
Pay careful attention to the error messages. It’s not uncommon to uncover email server and/or
network configuration issues when you’re setting up new email accounts."

Look carefully at your email configuration setup - use the ebase Admin Manual, Chapter 10, as a guide. Also, I've found where you have (directory) your plugins (make sure you have them, period) may make a difference.

Best... Tim Leed