Oh yes, I see.
It's a firefox-only thing, in other browsers it is working fine.

This seems to be a problem caused by the company that I use for the certificates. I hope that it will be resolved within 24 hours.
In the meantime, use another browser or go to Menu->Options->Advanced->Verification and turn off the checkbox that says 'Use the Online Certificate Status Protocol'



The GitHub repository is now set up, by the way:

https://github.com/Qqwy/LastMail


Also, users using Tor, noscript or a similar JavaScript-blocking service should also be able to use the system. They won't be able to use the nice WYSIWYG HTML mail editor, of course, but they can still make text messages or write the html code themselves. The system is fully functional without JS.

~W-M