mailtransfer
Mail transfer is the process by which electronic mail is moved from a sender’s mailbox to a recipient’s mailbox across computer networks. It is mediated by mail transfer agents (MTAs) that relay messages between servers, typically using the Simple Mail Transfer Protocol (SMTP) for inter-server transfer. Mail transfer is distinct from local delivery, which places the message into the recipient’s mailbox on the final server and is usually performed by a mail delivery agent (MDA).
Overview of operation: a user composes a message in a mail user agent (MUA) and submits it
Security and authentication: transport between MTAs is commonly encrypted with TLS and supports STARTTLS to upgrade
Implementation and terminology: Popular MTAs include Postfix, Exim, Sendmail, qmail, and commercial solutions such as Microsoft
By coordinating these components, mail transfer enables delivery from senders to recipients across the Internet, subject