Microsoft has released a patch for an issue in Windows Mobile 6.1 where an email account could become corrupted and be unable to send emails using POP3 or IMAP4. The problem arose if a mobile operator did not provide an alternate SMTP server name and if the device could not connect.
The patch is available in both CAB and MSI formats.
Keep this patch somewhere handy as it will likely be wiped off should you have to do a hard reset on your device later on.
Note: This issue does not affect Windows Mobile 6.0 devices.