This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Este fío arquivouse. Faga unha nova pregunta se precisa axuda.

Slow and unresponsive IMAP because of Antivirus

  • 3 respostas
  • 1 has this problem
  • 1 view
  • Last reply by Stans

B4net
B4net
more options

Thunderbird v.91.2.1 Windows 10 Windows Defender

Here we have around 10 computers using TB with IMAP account. All updated to latest Win10 and latest TB. For some time(around 2 months) we are experiencing extreme lagging each morning after Thunderbird start. If one of computers was not synchronized for a week the TB freezes for more than 3 hours downloading latest 1000 e-mail in Inbox. It is not possible even to close the TB. The same is in safe mode with disabled addons.

Luckily I found the reason today. Antimalware service (Windows Defender) was using 12% of CPU while TB was lagging/frozen. I disabled the Win Defender and instantly the e-mails were downloaded and TB was running fine. I repeated the situation and I can repeat the problem any time.

Strange thing is, that one of computers still uses TB v.78.14.0 Windows updated but the TB on that version hasn't got any problems with Antivirus. I assume, the problem lays somewhere in the new versions of TB like 91.x.x.

I think an option to go around that is to disable real-time virus protection for TB profile location, which I don't like. Is there a safely known option to go around that thing in new version of TB? Thank you!

Thunderbird v.91.2.1 Windows 10 Windows Defender Here we have around 10 computers using TB with IMAP account. All updated to latest Win10 and latest TB. For some time(around 2 months) we are experiencing extreme lagging each morning after Thunderbird start. If one of computers was not synchronized for a week the TB freezes for more than 3 hours downloading latest 1000 e-mail in Inbox. It is not possible even to close the TB. The same is in safe mode with disabled addons. Luckily I found the reason today. Antimalware service (Windows Defender) was using 12% of CPU while TB was lagging/frozen. I disabled the Win Defender and instantly the e-mails were downloaded and TB was running fine. I repeated the situation and I can repeat the problem any time. Strange thing is, that one of computers still uses TB v.78.14.0 Windows updated but the TB on that version hasn't got any problems with Antivirus. I assume, the problem lays somewhere in the new versions of TB like 91.x.x. I think an option to go around that is to disable real-time virus protection for TB profile location, which I don't like. Is there a safely known option to go around that thing in new version of TB? Thank you!

All Replies (3)

Stans
Stans
more options

There's really no harm in adding Thunderbird's profile folder to Defender's exclusions list. In fact, that's exactly what you should do if you don't want your AV interfering with Thunderbird's normal functioning. It is NOT Thunderbird that is interfering with your AV. It is the AV that is messing with Thunderbird's normalcy, so there is no option in Thunderbird to go around your AV. Also, if there was such an option, don't you think it would effectively be the same as excluding Thundebird from the AV's protection scope?

B4net
B4net Question owner
more options

I will try that option Stans if there is no other options. But I still cannot understand why would the same updated Windows Defender Antivirus treated Thunderbird profile from TB version 78 different as profile from TB version 91. I have in front of me two computers with different TB versions, the same Antivirus versions and same updated Windows 10. Computer with TB v78 is not affected with TB freezing. That is strange.

Stans
Stans
more options

B4net said
But I still cannot understand why would the same updated Windows Defender Antivirus treated Thunderbird profile from TB version 78 different as profile from TB version 91.

The answer is quite simple. TB 78 and 91 are NOT exactly the same. Under-the-hood changes in code and behaviour are inevitable for an actively developed product like TB.

I have in front of me two computers with different TB versions, the same Antivirus versions and same updated Windows 10. Computer with TB v78 is not affected with TB freezing. That is strange.

Not strange at all. AV have had a long history, long before TB78 and Defender, of messing up with TB. See https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues