Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

When I attempt to rapidly delete a sequence of emails in Thunderbird that have arrived in the Inbox using the Delete button on the keyboard, Thunderbird freezes for about 5 full seconds for about 1 out of every 4 emails. The other 3/4 delete immediately.

I also use Nostalgy to allow me to move emails from the Inbox to another folder with the press of a single key, and the exact same problem occurs in that case.

I have run Thunderbird in Safe mode, and disabled my Avast antivirus program's "real-time shields" (including mail shield), and neither has fixed the problem.

Also, I quit Thunderbird & deleted all .msf files, and it did not resolve the problem. I attempted to compact my folders, but absolutely nothing happens when I right-click a folder and select "Compact".

Please note that I regularly synchronize the entire Thunderbird folder to online storage and to other workstations, but I never run Thunderbird simultaneously from multiple workstations.

Please help! This problem is becoming so much of a nuisance that I am seriously investigating other email clients. Thank anyone in advance for any suggestions.

share|improve this question
Your question lacks vital information necessary for a real answer to it. Is it local mailbox? Or a POP3 mailbox? Or an IMAP mailbox? What (since this is configurable) have you configured Thunderbird to do when you press the delete key? – JdeBP Jun 27 '11 at 9:03
It is a POP3 server and the mail is downloaded onto the local machine. The delete key moves the item to the "Trash" folder, which is the default. – Dan Nissenbaum Jun 27 '11 at 15:33
I suspected as much. There's no such difficulty with IMAP (and where there is it's a server-side issue). – JdeBP Jun 28 '11 at 9:33
up vote 2 down vote accepted

Thunderbird uses a slightly modified version of the mboxrd mailbox format for local mailboxes and POP3 mailboxes. The mbox family of mailbox formats is highly inefficient anyway when it comes to expunging messages from and inserting messages into a mailbox. Expunging requires rewriting the entire file from the expunged message onwards. Inserting means at the very minimum seeking to the end of the file and writing. And that's ignoring the additional operations on the summary database.

Combine this with Thunderbird's normal method of deleting messages from mbox files, which is to set a flag in the X-Mozilla-Status: header and leave the message in the file until it is compacted, and things can become very slow. A mailbox with a large number of deleted messages may appear nearly empty, but operations upon it will be slowed down by all of those deleted messages, because as the mailbox file is written and rewritten all of those deleted messages will continue to be included, until the file is compacted.

The rest of the world, including most of the IMAP servers that you won't see exhibiting these problems, has junked the mbox family of mailbox formats long since, precisely because it is slow and fragile in these ways. Several use some variant on the Maildir format, where expunging a message is as fast as deleting an ordinary file from a directory. Some MUAs use Maildir, too.

Alas, Thunderbird users are stuck with mbox. There have been calls for Thunderbird to employ Maildir since at least 2004, possibly earlier. Unluckily for Thunderbird users, after all these years it still hasn't happened.

share|improve this answer
Do you know of a good alternative to Thunderbird that is easy to back up and restore, that allows a single key to be pressed to move a message into a different folder, and that uses the Maildir format? – Dan Nissenbaum Jun 29 '11 at 4:19
Also, if I use IMAP instead of POP with Thunderbird, will this resolve the problem? – Dan Nissenbaum Jun 29 '11 at 5:53
You're best off asking "Is there an MUA that uses Maildir that also has features X, Y, and Z?" as a separate question in its own right. Don't forget to tag it as "maildir". – JdeBP Jun 29 '11 at 10:01
We already have questions such as "What are the differences between POP3 and IMAP?", note. So check out all of them, first. – JdeBP Jun 29 '11 at 10:05

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .