Cannot send email messages to Yahoo server

Yahoo requires an "app password" for 3rd-party email apps like Thunderbird when using Normal Password authentication. This is distinct from your regular login password. See the following articles:

IMAP server settings for Yahoo Mail https://help.yahoo.com/kb/SLN4075.html

Generate and manage 3rd-party app passwords https://help.yahoo.com/kb/generate-manage-rd-party-passwords-sln15241.html

Although they don't mention it here, Yahoo can also use OAuth2 authentication. In that case, you use your regular password when prompted, not an App Password.

If you use OAuth2, make sure cookies are allowed in Thunderbird.

Also, if you have multiple Yahoo/AT&T accounts in Thunderbird, you may have to make an additional chang to Thunderbird to work with Yahoo's newer security protocols, as detailed in this article:

OAuth2 Authentication for Yahoo, AOL and ATT https://support.mozilla.org/en-US/kb/thunderbird-and-yahoo

Lin, This whole process is too confusing. Things are getting worse. My Mailwasher program is now also not working. I was able to sign on to Yahoo, but I don't know how that helped me. Running Thunderbird in trouble shoot mode got me no wheres. Using OAuth2 authorization, but reads of server fail. Not clear how to reload my Thunderbird from the Win64 directory. The only thing that seems to work is my AT&T email handler.

Using a password from my Mailwasher program, I was able to restore read and write abilities to Thunderbird with the normal password setting. However, I still have a problem accessing URL's from withing the Thunderbird emails. Now, I cannot set Thunderbird as the default email handler. I try to turn it on, but it does not accept it. Using your instructions to switch to another client, like my Google, I cannot add it to the list of Default Search engines. Adding process asks for the URL of the OpenSearch provider and I don't know where to find it in my Google specs.

re :However, I still have a problem accessing URL's from withing the Thunderbird emails.

That is a different question, it does not even have a relationship to server settings query and therefore it should be asked in a new question. But....url links in an email in Thunderbird, need to use a browser to open those url webpages in a new tab.

Thunderbird and computer use the browser you have set up as default. What browser : eg: Mozilla Firefox, have you set as default on your computer?

re :Now, I cannot set Thunderbird as the default email handler. I try to turn it on, but it does not accept it.

You can set up to check within Thunderbird and it's worth switching it on.

• 'Settings' > 'General', under 'system integration'
• select checkbox 'Always check to see if Thunderbird is the default mail client on startup'

But you set up default apps on your computer. You need to set up Thunderbird as the default Mail app on your computer. If Windows type 'default apps' in search and set it up.

As Toad-Hall mentions, the clickable links thing is a Windows issue, not Thunderbird's. Thunderbird relies on Windows to tell it what to do when it encounters a web link. It is unrelated to your Yahoo issue, which I understand is now working correctly.

If Windows 7 doesn't let you change the defaults for Firefox, it's because it already is the default. However, Windows can get confused, especially earlier version like Windows 7, which is why it can help to "tickle" it by changing the setting to something else, then back to the original. If you don't have a second web browser installed, Internet Explorer is still available. It's useless as a web browser, but for this purpose it will do. If it's not currently installed, got to Windows' <Control Panel | Programs and Features | Turn Windows Features Off or On> and turn on Internet Explorer 11. Now you can go back to <Control Panel | Default Programs> and change the default web browser to IE, then back to Firefox. This might help - I can't guarantee it.

Another possible factor is that some emails that are in HTML format are incorrectly coded so that web links are not clickable. This is the fault of the sender, not of Thunderbird or Windows. If you find that SOME emails have clickable links, but others from different senders DO have clickable links, this is probably the case. A workaround is to display the message in Plain Text format - Thunderbird will usually recognize the link on its own and make it clickable for you. To change the viewing format, in Thunderbird go to menu item <View | Message Body As...> and choose Plain Text. You may find that the links are now clickable.

Lin's fix to set the default email handler to something other than Thunderbird and then back again seems to have some how reset Thunderbird as the default. I can now see the URL's embedded in my Thunderbird messages. I can only imagine that cleaning off a Trojan Horse virus may have clobbered something. I hope this does not happen again. Thanks for the help.