[Users] claws-mail impap-error Port 993 tls on Macos

[David Fletcher]

>Apart from anything else, you are giving google a great deal of information
>about both you, and your recipient.

Using google isn't a choice - work IT is outsourced to them, I can't
change that.

After some more investigation I'm narrowing down the issue. I can now
reliably produce the fault, and work around it.

- This does not appear to be a TLS issue. It happens also with
connections that are configured without TLS.

- After starting Claws if I attempt an IMAP connection with TLS I get a
failed connection. Network log:  TLS handshake failed. Apple crash log
reports no entry for this.

- Next attempting a POP connection (also with TLS) it will work. This
sequence is repeatable with each Claws re-start. And once this is done
the POP connections just work normally for that session with Claws.

I think something is not being initialised properly. Attempting to set up
the IMAP connection sets things up so the next POP connection is fine.
This is very strange since these are quite separate code areas within
Claws. It seems like the kind of thing that happens with pointers
accessing non-initialised memory. Initially the memory content is random
or overwrites another process, but later becomes predictable, even if
not obviously connected within the code.

I'll continue to explore things. This could be an Apple library fault.
Also, their documentation mentions "Pointer authentication can also
expose latent bugs in existing code" - maybe that's happening here? It
might also be very arm64 specific.

David.