sqwebmail can't write to /var/cache/sqwebmail, permissions broken

[Stephan]

reproduced on a fresh install of Ubuntu 18.04.1 LTS

sqwebmail:
  Installed: 5.9.0+0.78.0-2ubuntu2

After user logs in to webmail a failure is reported in mail.err:

sqwebmaild: maildircache: Cache create failure - unable to create file /var/cache/sqwebmail/274813/us/user.

this is caused by /var/cache/sqwebmail having the wrong owner:
rwx------ 2 courier courier 4096 Sep 23 17:57 sqwebmail/

during configure step of sqwebmail the owner of the cache folder is specified. Upstream uses "bin" here:
https://github.com/svarshavchik/courier/blob/master/sqwebmail/sqwebmail.spec.in#L31

So either change during build to use a different owner, e.g. "courier", or change the owner of the /var/cache/sqwebmail folder to "bin".

As a workaround manually changing the owner to "bin" makes webmail to properly use the cache.

[Stephan (world-wide)]

The problem still exists in Ubuntu 20.04.3 LTS.
Workaround of changing owner of cache as described will still restore functionality of sqwebmaild.

As upstream still uses "bin", I suggest to change the owner of the cache folder.