Linux · Mail Server: Postfix

opendkim-testkey -vvv reports 'key not secure' on one run and 'record not found' on another. Which is harmless and which is a real problem?

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More in Mail Server: Postfix

A colleague says the mail transfer agent is the whole email server and drops mail into users' inboxes. Where is that wrong, and what actually does the local delivery?

In mail-server terminology, what do MUA, MDA, MTA, and SASL each stand for, and which one is the client program the user actually sees?

A user wants their mail to stay in sync across a laptop, phone, and tablet. Between POP and IMAP, which fits, and what is the core difference that decides it?

You are configuring a mail client and must pick the right port. Which port is for server-to-server SMTP, and which is the submission port that clients should use to send mail?

When storing incoming mail, what is the practical difference between mbox and maildir format, and which one is recommended alongside an IMAP server?

You add an entry to /etc/aliases to redirect root's local mail to your own account, but nothing changes. What step was missed?

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