You need to whitelist the adress/domain on your mailserver.

It's either my webmail mail server or a mailing list mail server. Neither has a whitelist function. So, I'm contacting their support. Thanks.

So how do I fix? My friends emails always go to junk mail and I don't know how to prevent this in Thunderbird.

So how do I fix? My friends emails always go to junk mail and I don't know how to prevent this in Thunderbird.

If your friend has "enable junk mail controls for this account" checked, uncheck it (in properties, w hich you get to by right-clicking the account name).

If it is unchecked, and it is not your friend's email that is being marked as junk, and it is email being received by your friend's webmail provider (e.g. startmail, hushmail, etc.), and if the webmail provider has a whitelist, whitelist the emails being marked as junk.

If it is your friends email that is being marked as junk and your friend is using a webmail provider, your friend might be experiencing my problem, which is that either my webmail provider or a mailing list is marking my emails as junk. I still haven't gotten an answer from either of them. The webmail provider at least responded and is investigating.