Dovecot doesn't have write permissions?

I tried changing the line in dovecot to this:

mail_privileged_group = mail

then restarting postfix and dovecot. No change.

Do you have a user called vmail and does it have a directory /home/vmail? I had to have that.

I don't, but I tried chmod 777 /var/mail and there was still no change.

I then went through and applied chmod 777 to every subdirectory manually, like this:

chmod 777 /var/mail
chmod 777 /var/mail/vhosts
chmod 777 /var/mail/vhosts/DOMAIN.com
chmod 777 /var/mail/vhosts/DOMAIN.com/USER1
chmod 777 /var/mail/vhosts/DOMAIN.com/USER2
chmod 777 /var/mail/vhosts/DOMAIN.com/USER3

And this worked! Why would that be? Shouldn't the permissions from /var/mail cascade down to all the subdirectories? Isn't that what the 's' in the permissions flags means?

I'm using MySQL for user auth and virtual domains so I don't want to tell you wrong. Perhaps someone on here who has a similar configuration to yours can advise further.

It looks like the problem was that all the subdirectories somehow had different permissions than /var/mail despite the s flag in the /var/mail permissions. I was able to fix the problem by going through and setting all their permissions manually.