An MTA is a program like Sendmail or postfix, and is used to transmit e-mail messages via SMTP. It's an important component in setting up your own mail server,

An MTA is a program like Sendmail or postfix, and is used to transmit e-mail messages via SMTP. It's an important component in setting up your own mail server, but it doesn't speak the POP3 or IMAP protocol. For serving IMAP, one program I've had recommended to me is dovecot. I don't have personal experience with it, but I've heard good things. One solution I've considered is using dovecot on my local laptop, plus some custom scripting with imapsync (to sync the mailboxes), then something like mutt as a local IMAP client, and then imapsync would be responsible for syncing the changes made with mutt back to the upstream mail server. But I haven't done this yet, and I haven't done that much research into what all components would be required to make this work well.