When accessing Roundcube you will receive an error that says "Server Error" and when checking the Dovecot log file (
/var/log/maillog) you will see entries similar to the ones below:
Error: i_stream_seekable_write_failed: close((&sstream->fd))
@ istream-seekable.c:251 failed (fd=19): Bad file descriptor
Panic: file istream-seekable.c: line 231 (read_from_buffer):
assertion failed: (*ret_r > 0)
These errors signify that temporary Dovecot files cannot be written. This can be the result of the
/tmp directory being at 100% disk space used.
Check the contents of your
/tmp directory and confirm if there is space available to be used.