Have you checked to see if thunderbird is marked in offline mode? lower left of main screen will show onlline or offline if status bar is active. If not, click view>toolbars and tick status bar. also check file>offline to see if that is set. And PLEASE do not post the same issue TWICE. It causes unnecessary confusion. Thank you

I am not familiar enough with this system to know if I post an issue twice, or whether it could be posted to two different forums.

There is nothing I can find about any off line mode. I saw this in another post too, and I have no idea what it refers to. I just went to view, toolbars and a sidebar comes up, but still I see no icon saying offline mode.

But then, I had decided to close the program and reopen it again, and "send" returned. Very confusing. Does this link/icon only appear when thunderbird is "offline"? And how did it get "offline" in the first place?

I wish people who reply here can refer questions to whoever actually writes the program, and such writers should be available for feedback. Thanks for your reply, though!

Since this side-issue of how to contact the programmers remains forever unsolved, apparently, and having not seen any "offline" icon anywhere, I will not mark this issue "solved", even though I "solved" it myself just by closing and re-opening the program.

I mean "send" returned above, when I closed and re-opened the program. Sorry for my typo.

I saw no "delete" option for this comment.

This is one forum, not multiple, and you've posted here before. You cannot expect to talk to developers for a free software app. Even if you pay thousands of dollars for an app, the developer is not available for discussion. Anyway, I'm glad it's working. I will appreciate it you mark both posts solved, so that others don't waste time reading them. thank you.

Your term "developers" seems to me to refer to the original programmer of an app. But the problem is usually when a change is made. Yes, I think users and for that matter those who answer this forum should be able to contact whoever makes a change to a program about a possible bug or unfortunate or mistaken change made.

My questions about why "send later" appeared instead of send, and why there is no "offline mode" link you referred to, were not really answered. Others might like to know, in case you or anyone else have any info about it.