Sometimes, emails cannot be sent

Sometimes, I write an email, press on ‘send’, and nothing happens, not even an error message. This is very annoying.

One further behaviour: I fetched the email from the Drafts directory, and then I could send it.

Which version of the app are you using? Has this happened with older versions? When did it start?
Does it work after pressing the send button again?
Is there any pattern? Does it only happen with replies? Does it only happen after adding an attachment?

I am using version 6.309.
This has not happened in the past, but I do not know when it started. When this happens, I can press the send button as often as I want, but nothing happens.
I see no pattern for this. The last time it was a reply without an attachment, but I do not have any information whether this is necessarily the case.
The problem is that this does not show reproducibly: I replied for example twice to an email. The first time, nothing happened. The second time, this behavior was shown. The error happens not every time.

Today there was another example. Also a reply, but this time there was an attachment.
After sending was silently refused, I pressed ‘back’, then there appeared a message wheter I weather I wanted to store it as a draft (‘yes’), and then I could send this draft.

In K-9 Mail 6.309 code has been added to ignore clicks on the send button after sending the message has already been triggered. This is to avoid double clicks sending two messages.

I don’t see how it is possible for the variable that keeps track of whether or not send has already been triggered to be true when the send button hasn’t been clicked yet.
If you’re using a crypto provider, there is a chance trying to send the message silently fails, and then subsequent clicks on the send button will be ignored. But that means the first click on the send button would sometimes not have worked in older versions either.

I’ll fix the code to allow clicking the send button again after a (silent) send error. I don’t quite understand what needs to happen in order to run into a situation where sending a message would silently fail. I’ll add some logging so we can hopefully track down this problem in the future.

Just to add a different perspective. In past versions of k9 I had that problem too. But lately (at least last 9 months) it no longer happens. Should add that I do not / never did use IMAP on any mail account.