I am having the following error on my logs.

log error:
This does not make sense to me. /webserver and everything inside is owned by developer (uid=500).

I used mail_uid and mail_gid in dovecot.conf to set the permissions, I'm not using local system accounts, instead accounts specified in MySQL.

I can dump all the output of doveconf if requested.

Any suggestions ?

You do have a permissions problem. I am not certain exactly what the cause is, but I notice that it is trying to create the maildir in a strange location. Specifically, /usr/local/var/run, which I have never heard of /var being off of /usr/local. Instead /var is a root level directory that holds variable information and /var/run holds pid (process ID) files for running applications. Consequently, this isn't a place you want to put your mail.

It may be that you are running into a groups or ownership permission for the dovecot application, but I suspect that you have something mis-configured. Did you compile the applications yourself or did you install from a repository?

It turns out I had:
...when I should have:
See the space after maildir:
that was the result of copy and paste.