https://support.mozilla.org/en-US/kb/cannot-send-messages#w_verify-that-your-outgoing-email-is-not-being-blocked

        duncanst

bbrewer3, If AOL is your ISP, see below for a correction. duncanst I tried the below fix from Bo445 and it corrected the problem. Thanks Bo445! Bo445 7/15/21, 1:40 PM more options Found this info below on https://downdetector.com/status/aol/. I used it and my AOL/Verizon incoming and outgoing mail now works. You retain your existing webmail password, and generate a new one for your Thunderbird in- and outgoing mail. Thunderbird users, listen up. We have to enter a new password for incoming & a new password for outgoing. Go out to AOL web site, then click-on AOL Mail, then click-on "Options" in the upper right, under your email address. Go to Account Info Go to Security (list on the left) Scroll all the way down to "Manage App Passwords" Generate a code for "other" by inputting "Thunderbird" Copy and save it to clipboard. Go back to Tbird. Click on 3 bars in upper right, then "options" Then "privacy and security" Scroll down to "saved passwords" Delete the old ones. Attempt to receive emails. When prompted, give Tbird the new password. Make sure to check "manage with password manager," or something like that. Then do the same for sending an email. So, go back into the AOL web site (AOL Mail) and create a 2nd Manage App Password for Outgoing e-mails. Give it a different name from your 1st AOL App Password (maybe name it Thunderbird Out). Check to make sure the "saved passwords" have one for incoming & one for outgoing. (ht to DeborahFeller and MegansUncle2)