SMTP after POP
SMTP-after-POP or POP-before-SMTP is a method for restricting the sending of e-mails , in which the Simple Mail Transfer Protocol (SMTP) is made dependent on the Post Office Protocol (POP), which is only used for downloading E-mails, but allows authentication .
Authentication for sending e-mails was not originally intended and long controversial, but was ultimately accepted because of spam and led to SMTP Auth .
With the older SMTP-after-POP, a mail server only accepts e-mails if the sending IP address has previously called up e-mails using POP, login and logout within a certain time window . Usually such restrictions are limited to dynamic IP addresses on the Internet . Since it is not possible to infer a specific user from an IP address due to Network Address Translation , this procedure only provides an indication that a specific user is actually active.
Individual evidence
- ↑ RFC 6409: Message Submission for Mail . Internet Engineering Task Force . P. 7/8. November 2011. Retrieved February 28, 2013.