Mail IMAP weirdness (duplicates, not downloading)

Question

Hi there,
I've used the Mac Mail app very happily for several years now, at home and at work, to access both my .Mac email and my work-based IMAP mail.
Last week, our IT team moved my email account to a new mail server, and ever since, I've been experience very very weird and intermittent problems receiving and reading my IMAP mail (the .Mac mail is fine).
These problems manifest as:
* On startup, it sometimes takes many minutes before new messages are displayed in my Inbox. Sometimes they will appear and disappear several times before 'stabilizing'. Frequently, messages that I have already read will disappear and reappear as 'new'.
* Occasionally, and with no warning, some messages will start to 'replicate' themselves..I can end up with multiples of 5 or 6 of some messages (but not all) in my Inbox.
* Occasionally, I am simply unable to view a message. The message appears in my Inbox, but when I try to open it I see a message telling me I need to go online to download the contents of the message, even though I am online. Sometimes when I'm trying to open one of these messages, the account seems to flicker offline and online and offline again.
There seems to be no rhyme or reason to this. It's intermittent and unstable. The IT guy insists it must be the Mail app (I'm the only Mac user), but everything was fine before...
Suggestions? Settings I can check?
Thanks.

Answer 1

Hi LeahMac.
Go to Apple Menu > System Preferences > Network, choose Network Port Configurations from the Show popup menu, and make sure that the configuration used to connect to Internet appears at the top of the list. Leave checked (enabled) only the port configuration needed to connect to Internet and Built-in Ethernet (in that order if not the same), uncheck (disable) the rest of network port configurations and see whether that helps — if it doesn’t, turn ON again the ones you want enabled.
Try using a different method to connect to Internet, if possible, or connecting the computer to Internet as directly as possible (i.e. bypassing any routers that might be present, using an ethernet cable instead of wireless, etc.), and see whether that makes a difference.
Do you have any custom rules? Try disabling all the rules and rebuilding the mailbox afterwards, i.e. select the mailbox in Mail and do Mailbox > Rebuild.
Do you have any Mail plug-ins or system utilities that could interfere with Mail? In the Finder, go to each of the following folders (if they exist). What do you see there?
/Library/StartupItems/
/Library/LaunchDaemons/
/Library/LaunchAgents/
/Library/InputManagers/
/Library/Mail/Bundles/
~/Library/LaunchAgents/
~/Library/InputManagers/
~/Library/Mail/Bundles/
To make accurately reporting this information easier, you may open /Applications/Utilities/Terminal, type the following command (you can just copy it here and paste it in Terminal), and press <Return>. You can then copy the output of that command from Terminal and paste it in your reply to this post:
ls -1 /Library/StartupItems /Library/LaunchDaemons /Library/LaunchAgents /Library/InputManagers /Library/Mail/Bundles ~/Library/LaunchAgents ~/Library/InputManagers ~/Library/Mail/Bundles
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder. You can easily locate any of the folders referred to in this post by copying the folder path here, doing Go > Go to Folder in the Finder, and pasting the folder path there.