As the email client on the N810 is the same one used in OS2007 I bet it's having the same problem: If for any reason the sub-process that's connecting to the mailserver has problems, then it won't launch. This could be a) a config problem, as in when using the wrong port for gmail/imap/imapSSL connection, or b) just because your network was disconnected just the moment the osso-email app tried to sync email. After that it won't launch the emal application.

The fix is to enter 'killall enprocess' in xterm, after that the email app should start. If it never does, then it's a configuration problem as indicated above.

I have load-applet-run installed in OS2007. It has an option for executing commands directly, I entered 'killall enprocess' and ticked the 'save' option, called it fix-mail and I just click it whenever the email hang problem happens. It'll exit with 'exit code 0' if it indeed killed the enprocess sub-process. This fixes the hang problem every time for me. (But as I said, the config has to be correct first.)