What is the issue?
ITS has identified some problematic behavior in the Thunderbird email software versions 1.5.x and 2.0.x. Moving or deleting more than 200 messages at once can make your email software respond very slowly, and could even cause it to crash.
What can I do to solve this problem?
You just need to change the Connection timeout to 1500 seconds:
Windows XP and Vista
To change the Connection timeout to 1500 seconds using Windows XP and Vista:
- Open Thunderbird.
- See what version of the software you are using. Learn how to find what software version you are using.
- If you are using version 1.5.x:
- From the Edit menu, select Preferences.
- At the top of the window, click the Advanced icon.
- Click the General tab.
- Change the Connection timeout to 1500 seconds and click Close (see Figure 1).
- Close Thunderbird, and then restart it.

Figure 1.
- If you are using version 2.0.x:
- From the Tools menu, select Options.
- At the top of the window, click the Advanced icon.
- Click the Network & Disk Space tab.
- Change the Connection timeout to 1500 seconds and click OK (see Figure 2).
- Close Thunderbird, and then restart it.

Figure 2.
- Now you can move or delete more than 200 messages at once.
Mac OSX
To change the Connection timeout to 1500 seconds using Mac OSX:
- Open Thunderbird.
- From the Thunderbird menu, select Preferences.
- At the top of the window, click the Advanced icon.
- Click the Network & Disk Space tab.
- Change the Connection timeout to 1500 seconds (see Figure 3), then close the window.

Figure 3.
- Close Thunderbird, and then restart it.
- Now you can move or delete more than 200 messages at once.