I am sorry to add to the confusion. I am wrong and you are probably right. I have also sqwebmail-curcache in my maildirs. There is no /var/sqwebcache on my system anymore. My information seems to be outdated, I've been using sqwebmail for many years.

My system uses the same account "vmail" for all virtual mail operations. I have set it up in authldaprc using LDAP_GLOB_UID and LDAP_GLOB_GID. As long as all the maildirs are readable and writable by vmail only everything runs smoothly. Nobody has shell accounts on the mail system.