Microsoft Patches Windows Mobile 6.1 SMTP Bug
Microsoft has patched the bug in Windows Mobile 6.1 where the email database could become corrupt and you are unable to send emails via POP3 or IMAP4 through an SMTP server. Outlook/Exchange emails, as well as SMS/MMS messages were unaffected.
"This behavior is associated with a feature that is introduced in Windows Mobile 6.1. The feature allows for mobile operators to specify an alternate SMTP server name that is used if e-mail messages cannot be sent by using the user-specified SMTP server name. If the mobile operator does not specify an alternate SMTP server name and if the Windows Mobile 6.1-based device does not connect, the e-mail account is corrupted and cannot send e-mail messages."
More at: Smartphone Thoughts: Microsoft Patches Windows Mobile 6.1 SMTP Bug and Windows Mobile 6.1 SMTP Issues.
Download is here: WM 6.1 POP and IMAP Send Mail Patch