SMTP

SMTP (Simple Mail Transfer Protocol) is the protocol used for sending email. It moves a message from the email software on a device to a mail server, and then from one mail server to another.

How an outgoing email travels

1. Your email software uses SMTP to send your message to your mail provider's outgoing mail server.
2. That server uses SMTP to relay the message to the recipient's mail server.
3. The recipient's mail server stores the message until the recipient retrieves it.

For example, you send a message with a photo attached from a tablet. Your email software uses SMTP to send it to your provider's mail server, which relays it to your school's mail server. The message and its attachment wait on that server until they are collected.

SMTP sends, but it does not retrieve

SMTP has one job: sending. It does not fetch incoming messages or attachments from a remote mail server. That retrieval job belongs to POP3 or IMAP, which fetch messages and attachments from the mail server. If you are collecting an email that is waiting for you, SMTP is not the protocol doing that work.