Hi,
POP is used for receiving messages & SMTP for sending messages. So what does 'use POP before SMTP' do?
In any case when the user logs into his mail, all mails are downloaded first & then sent. Can someone please differentiate the workflow with & without this option?

Thanks in advance

In a mail system using POP and SMTP servers, checking mail on the POP server first and then sending queued mail to the SMTP server is quite common. If properly set up you need to authenticate to send mail as well as receive it. Often a POP system is set up so that if you have already authenticated to the POP server, you don't have to re-authenticate to the SMTP server as long as you're logged into the POP server.

Hi,
Thanks for the response. Is this procedure transparent to the end user? How will the end user know that POP is being used before SMTP?
Thanks

The process is usually completely transparent.

It isn't so much that checking POP before sending is required, but that when the SMTP server is configured to require authentication to send mail, if you have already accessed the POP server it usually uses that authentication as valid authorization to send.

If you ARE asked for a password/authentication by the SMTP server when you try sending mail without checking on the POP server first, but are NOT asked for a password to send if you check POP first then the system is using POP before SMTP to authenticate outgoing mail server access.

POP before SMTP is used primarily as a means to limit SMTP server use to network users and prevent spam relaying.

Thanks, for the reply. Consider the first scenario where there is no POP3 before SMTP
In this case, mail is directly sent to the recipient without any authentication
Second Scenario: POP3 before SMTP
It authenticates POP3 mail server using username & password & then sends a mail
How can this prevent spam?
Thanks