Changes

Postfix is capable of performing the function of an LDA but it has limited configurability, and only supports the MBOX mail storage formatis generally not used for that purpose. Currently the most popular LDA is LMTP but we'll use dovecot-lda because it's also pretty popular and we'll later be setting up Dovecot as an IMAP server. Using the two as a pair will increase the performance of your IMAP server.