Mailspring: Bug: Synchronisation fails (always)

[oddjobz]

Describe the bug

Client attempts to synchronise email, managed to accomplish quite a lot, but eventually stops and reports that the client is no longer connected to the server and prompts for a retry.

To Reproduce
Steps to reproduce the behavior:

1. Start mail client
2. Wait for .. up to 30 mins for red "disconnected" box appears

Expected behavior
All mails should sync leaving the client functional, rather than disconnected and non-functional.

Screenshots
n/a

Setup: (please complete the following information):

• OS: Ubuntu 18.10
• Mailspring Version: 1.7.8 (.deb)
• Mail server is Zimbra, although I've seen the same problem against Dovecot in the past

Additional context

The mailsync log shows this following a failure;

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* Mailspring Sync
A C++ exception occurred during program execution:
** database is locked

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21660 [2020-10-30 02:58:24.870] [foreground] [critical] * Stack trace (line numbers are approximate):
??:? exceptions::logCurrentExceptionWithStackTrace()
??:? runForegroundSyncWorker()
main.cpp:? runBackgroundSyncWorker()::{lambda()#1}::operator()() const
main.cpp:? _Bind_simple::operator()()
main.cpp:? thread::_Impl::_M_run()
** thread.o:? execute_native_thread_routine()

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I have tried mailspring many times, I have always had this problem and given up. This time I looked in the logs and can clearly see an issue .. so .. this is reproducible, every time.

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