If you have any thing eg: Anti-Virus scanning outgoing messages then Thunderbird may be stuck waiting for the Anti-Virus to release the file. Hence not responding temporarilly.

It can also take longer if you have attached a file to the email. Please remember all emails will increase in size as sending a binary file as a attachment increases its size by a third due to base64 encoding sending two 8-bit characters as three 7-bit ASCII characters.

As a heads up- example : if you have attached a file of say 15MB, in reality email will actually be closer to 21MB in size.

You could check your Anti-Virus settings and stop it from scanning out going mail which should improve things. You could also stop the Anti-Virus from scanning any thunderbird profile folders and files contained therein. After all, you do not need the AV slowing things down by scanning anything that gets opened to read and write files. You also do not need the AV messing around with any file. The AV programs have no idea that a single mbox file might contain hundreds of emails, so if you do let it scan your profile/emails etc do not allow it to fix anything as you stand a good chance of losing a load of emails.

Also please note it you use imap then there is also much jibber jabber going on between account and server.

Is the anti virus found via the thunderbird part? if so where is it please

The Anti-Virus is a separate program which you may have installed eg: AVG, AVAST, ESET, Norton 360.

OR it may be a default one supplied with the computer. Windows OS uses Defender by default and controls th Firewall https://www.microsoft.com/en-gb/windows/comprehensive-security

Some operating Systems have a default installed Anti-Virus but it might not be set up by default. Some info on a MAC https://support.apple.com/en-gb/guide/security/welcome/web

So how do i stop outgoing being scanned?

You need to offer some information. What Operating System you are using? What Anti-Virus product you are using?

I'm using Windows 10 pro with their built in standard virus & protect protection.

The info at the first link has information on how to exclude a single file or folder from antivirus scanning. You will want to exclude your profile.

• https://support.microsoft.com/en-gb/windows/add-an-exclusion-to-windows-security-811816c0-4dfd-af4a-47e4-c301afe13b26

Assuming you have Thunderbird profiles in the default location then you need to exclude this 'Thunderbird' folder to stop it scanning anything contained in it. C://Users/<Username>/Appdata/Roaming/Thunderbird

You say you have Windows OS pro In Win10 Pro edition or higher, you can access GRoup Policy.

Open "run" Type gpedit.msc

Once inside Group Policy Editor navigate to the following: Computer Configuration/Administrative Templates/Windows Components/Windows Defender/Scan Some people reported that in Win10 x64 Pro, it's the 9th option in the list from the top counting down. "Click on e-mail scanning" If this is already enabled then set the option to disable. click "Apply" on the lower right side, then OK. Remember after most Group Policy changes a reboot is required for changes to take effect even if windows does not ask for one.

Hi. It doesn't have "Computer Configuration/Administrative Templates/Windows Components/Windows Defender/Scan" on mine??