I had claws mail running in gdb. Woke up my laptop from sleep after 8 hours and clicked the button to receive all mails from all accounts.

gdb printed the following and claws hung:

[Thread 0x7fffc77fe700 (LWP 18392) exited]
/home/cweiske/.claws-mail/imapcache/127.0.0.1/cweiske/INBOX/69603: unlink: Datei oder Verzeichnis nicht gefunden

Program received signal SIGPIPE, Broken pipe.
[Switching to Thread 0x7fffdb9e4700 (LWP 11562)]
0x00007ffff60bf1d7 in __libc_send (fd=26, buf=0x7fffd40029f0, n=12, flags=-1)
    at ../sysdeps/unix/sysv/linux/x86_64/send.c:32
32	../sysdeps/unix/sysv/linux/x86_64/send.c: Datei oder Verzeichnis nicht gefunden.

(gdb) bt full
#0  0x00007ffff60bf1d7 in __libc_send (fd=26, buf=0x7fffd40029f0, n=12, 
    flags=-1) at ../sysdeps/unix/sysv/linux/x86_64/send.c:32
        resultvar = 18446744073709551584
        oldtype = 0
        result = -32
#1  0x00007ffff4f8648a in ?? () from /usr/lib/libetpan.so.15
No symbol table info available.
#2  0x00007ffff4f85f48 in mailstream_flush () from /usr/lib/libetpan.so.15
No symbol table info available.
#3  0x00007ffff4f9aa3a in mailimap_noop () from /usr/lib/libetpan.so.15
No symbol table info available.
#4  0x0000000000644bfe in noop_run (op=0x1c63950) at imap-thread.c:1074
        param = 0x7fffffffb9f0
        result = 0x7fffffffb9e0
        r = 0
#5  0x0000000000674fd4 in thread_run (data=0x1154700)
    at etpan-thread-manager.c:351
        do_quit = 0
        op = 0x1c63950
        thread = 0x1154700
        r = 0
#6  0x00007ffff60b7f6e in start_thread (arg=0x7fffdb9e4700)
    at pthread_create.c:311
---Type <return> to continue, or q <return> to quit---
        __res = <optimized out>
        pd = 0x7fffdb9e4700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140736877971200, 
                -9031597203050114831, 1, 140737354125408, 140737321375520, 
                4096, 9031657949053407473, 9031615177512407281}, 
              mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, 
            data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = 0
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
        __PRETTY_FUNCTION__ = "start_thread"
#7  0x00007ffff49d89cd in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113
No locals.