The Bat! v5.4 Home Edition keeps a message in outbox after it has been sent

I have been using The Bat! with Wine for a year, and has to switch to another mail client because of this bug.
After I send a message from Bat, the message remains forever in outbox.

Steps to reproduce

1) Create a GMail IMAP account in Bat
2) Write and send a letter

Expected behavior: The letter is removed from outbox after it has been sent
Actual behavior: The letter remains in IMAP outbox folder forever.

I don't have this problem when using Bat on Windows 7, so it must be related to Wine.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: wine 1.4.1-0ubuntu5
ProcVersionSignature: Ubuntu 3.8.0-26.38-generic 3.8.13.2
Uname: Linux 3.8.0-26-generic x86_64
ApportVersion: 2.9.2-0ubuntu8.1
Architecture: amd64
Date: Tue Jul 23 22:12:08 2013
EcryptfsInUse: Yes
InstallationDate: Installed on 2012-07-11 (377 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
SourcePackage: wine1.4
UpgradeStatus: Upgraded to raring on 2013-04-26 (88 days ago)