We have 3 known issues with Yahoo! Mail server:
1. [bizmail login] often gets into the wrong account. The is a yahoo mail server issue and has been reported to the yahoo mail server team. It's currently under investigation. There is no workaround at this point.
2. [Invalid UIDNEXT] which can manifest into different sync failure behaviors such as some messages not being downloaded from server or some messages not being uploaded to server. This is a server bug, so we have opened a bug with the yahoo mail server team and it's under investigation. For people who are blocked by this issue, we can pass on your yahoo ID and the server team will rebuild your mailbox to correct the problem. In order to verify that you are running into this problem, please follow the instructions below.
3. [outgoing message fails to go out] which is also a server issue. The yahoo server API we use for sending outgoing messages have some limitation. We have reported the issue to the yahoo mail server team and it's currently under investigation. If you are seeing this problem, please follow the instructions below to collect data to help us cover all cases.
Instructions for collection data for issues 2 and 3:
a) Go to account setup page of your yahoo account. If you are in the main UI you can find a link called "Account Setup" on the upper right corner, then click on the yahoo account in question.
b) Check the checkbox labeled "Enable debug trace" and save the change.
c) Go back to the main UI and do another sync by clicking "Send/Receive".
d) find the two log files under <install>/log: zdesktop.log and zdesktop.out. <install> is the folder where you chose to install Zimbra Desktop. File a bug and attach both as private attachments. Note please don't mark the bug as private, but mark the attachments as private. Attachments marked as private can only be viewed by zimbra employees. These two log files don't contain your yahoo password. To file a bug, go to Log in to Bugzilla and select "Desktop Client" as Component.