Which application determine or set the maildir in a mail server?

Question

My question is about mail server configuration with postfix (smtp) and dovecot (imap,pop3), both of these application have to see the same path to the maildir, for example /var/vmail/my_domain/user/Maildir. So, which application determine or set the maildir or the path to it?

Answer 1

In your case BOTH of applications sets the maildir path, but postfix define it for writing during local delivery, while dovecot define it for reading during POP/IMAP interactions.

This is an example of the bad configuration, widely spreaded over the numbers of howtos and manuals. You should never perform local delivery from the MTA like postfix or exim. You have to use LDA functionality from your POP/IMAP server like dovecot instead.

When you invoke dovecot's dovecot-lda for LDA then the single dovecot.conf is used to define storage path and the single service have r/w access to the sorage so you can secure storage by 600 permissions.

You can refer to the dovecot's wiki to know how to move LDA functionality from the postfix to the dovecot https://wiki.dovecot.org/LDA/Postfix