This is not a bug, more unexpected behavoir: If I try to send an email without a subject, Trojita displays an error that this is not possible. If it's actually not possbile to have an empty "Subject:" line (it it?!), I would propose to handle it like KMail does it: Warning about the empty subject line and let the user decide to add one or to send it anyway and add a generic subject like "(no subject)" automatically. I didn't look at the code yet, but I think that – if you want – I could implement this myself and file a ticket about it on Phabricator so you can merge it if you like it. Please tell me :-)
Thanks for your feedback. This is actually by design. We are not aware of a use case for sending e-mails with an empty subject. Technical reason: It breaks some e-mail threading algorithms. Opinion: There are certain patterns in e-mail usage which we like and "encourage" Trojita's users to follow. Writing e-mails with a subject is one of them. In my opinion, it's a good "etiquette" to provide a very short summary on what that e-mail is all about. Having usable subjects is something which makes navigation through thousands of e-mails more doable. Yup, everybody can just click that dialog away and enter "info" into the subject, but at least there's a reminder there. *** This bug has been marked as a duplicate of bug 331782 ***
It's of course meaningful to have a subject line. But just to mention a real-life example where I actually don't need one: I use and host a mailing list where a subscription or unsubscription is handled by sending an email to a specific address like list+subscribe@host or list+unsubscribe@host. It can be completely empty, because it's not parsed in any way, just the fact that an email has been sent to this specific address is processed. So, in this case, I have to add a dummy subject if Trojita is used for it. Of course, this is most probably a rare case, but at least, it's a real-life example ;-) I'll see if I can implement some lines of code improving the usability here and post them when I'm done.