Hello,
If the linux system is Centos 7.3...
which backend is good for working with ?
Well, if you're using mbox then what I said doesn't really apply.
As for a quota backend, check the Dovecot documents
What are you familiar with? How are you managing the email users? Maybe look for some email management package for Centos.
For instance I'm using a SQL database for the users and store the quota in SQL as well. I also had a need to specify different quotas for different users and the SQL web front end helped with that.
So I use the Dictionary SQL backend for quotas much the way it is outlined on the wiki
https://wiki2.dovecot.org/Quota/Dict But my choices may not apply to you. You could also use the dictionary with simple text files.
in my /etc/dovecot/conf.d/10-mail.conf:
mail_location = mbox:~/mail:INBOX=/var/mail/%u
how to config ? any post share in here ?
Thanks !
mbox is not the best way to setup a new mail server. Maildir is the simplest and most documented approach.
You might look for the Dovecot book by Peer Heinlein.
Most of this is really straying away from Roundcube.