What is SMTP?
SMTP (Simple Mail Transfer Protocol) is the standard communication protocol for sending e-mails. The SMTP server is the outgoing mail server of your e-mail account.
When you send e-mails, the SMTP server verifies the identity of the access. After successful verification, e-mails can be sent.
If an error occurs during the delivery attempt, the e-mail is returned to the sender with a corresponding error message. E.g. if the destination address is wrong, the error message is "address unknown" or "user unknown".
SMTP Port SSL encrypted: STARTTLS: 25/587 or SSL: 465