Schedule send solution add on won't add on
"There's a popular add-on for scheduling emails: https://addons.thunderbird.net/en-US/thunderbird/addon/send-later-3/"
I downloaded it, clicked, and Microsoft says it doesn't know what to open it with.
Wšykne wótegrona (3)
Addons are installed at Tools>Addons. On that pane is a gear icon with option to install from local files.
Installed, open the email, but the "send later" option is greyed out. I see no option to schedule the send.
You compose a message and enter an email id in TO field, and it's greyed out? You may need to ask the developer. I don't know the addon, but I would think it would stay grey until there was text and a recipient.