Thunderbird (also known as Icedove), is a great desktop email program, because it is well supported, full-featured, and free software.
Using Thunderbird with IMAP, however, can in some cases be very slow. Following are some suggestions for speeding things up:
- Using offline caching as described in this webchick article - in short: Tools -> Account Setting -> Offline & Disk Space -> Make the messages in my Inbox available when I am working offline
- Change Maximum number of server connections to cache to 1: Account Settings -> Server Settings -> Advanced… This seems counter intuitive (it would seem better to have more) – however, one cause of Thunderbird slowness is that it tries to connect multiple times and our server refuses those connections, which causes things to run more slowly than using one good connection.
- Keep your trash folder small. If you experiencing slowness deleting messages it may be because Thunderbird takes a long time to copy the message to your Trash folder. You might want to automatically delete your trash items on exit (in Account Settings -> Server Settings)
- For messages that you don’t want to keep (ever) – try holding the shift key while deleting. That will stop Thunderbird from trying to copy it to your delete items folder.
- Keep all folders small. Although the trash folder is a big one if you are experiencing slow downs when deleting, keeping all folders small will help in general. If you have folders with more than 1,000 messages you may experience slow downs when opening or moving messages. One way to accomplish this task automatically is to create a filter that moves all messages older than a certain number of days into an archive folder.
- Compact your folders that are slow – right click on the folder and select compact.
- If your messages are slow to open, try disabling your anti-virus software – the slow down may be caused by your anti-virus software taking a long time to scan the message (particularly if it’s a big message or has large attachments).
Many of these tips came from an excellent discussion of how to speed up Thunderbird’s IMAP functionality.