If you have an incoming SMTP mail feed, then the mail server sending mail to you will connect to your VPOP3 computer to send the mail. The mail connection is controlled by the sending computer.
If you have a permanent Internet connection with a static IP address, the usual way of having incoming SMTP is to configure your DNS 'MX' records to point to your external IP address. In this case, there are no changes needed to a normal VPOP3 configuration to allow this to work. You do NOT need to configure an SMTP Mail Collector in VPOP3. See Incoming SMTP Feed for more information.
If you have a dial-up connection, or other intermittent connection, or dynamic IP address, and your Internet Provider has provided you with an SMTP feed account, then, in this case, you may need to configure an SMTP Mail Collector. In these days of permanent Internet connections, this is rare!
You will need to configure an SMTP Mail Collector in VPOP3 if either:
If neither of these is the case, then you probably do not need to create an SMTP Mail Collector - see Incoming SMTP Feed for more information.
The descriptions of the settings below assume that you need an SMTP Mail Collector. Note that nowadays this is unusual. Usually, if you want incoming SMTP you do not need an SMTP collector!
With an incoming SMTP feed, VPOP3 does not control the flow of messages, so if it dials up to the Internet , it will usually not do anything to start the messages coming in. Usually the ISP will detect the connection and start sending messages to you. There may be a delay, so this option tells VPOP3 how long to wait for incoming messages to start.
VPOP3 cannot wait for ever because many ISPs who use this system will simply not start an SMTP session to VPOP3 if there are no messages to deliver, so it would stay connected for a long time unnecessarily.
If you set '60 seconds', then VPOP3 will wait for up to 60 seconds, then drop the connection if no incoming SMTP connection has begun (as long as its other connection tasks are complete). If an incoming connection has started, then VPOP3 will drop the connection as soon as the incoming connection has finished, whether this is within 10 seconds of the connection starting, or 3 hours.
Some Internet providers who provide an incoming SMTP feed via their servers require the use of the ETRN command. This is sent by VPOP3 to their server to tell it that VPOP3 is ready to receive messages by SMTP.
In this case, you should check the Use ETRN box, and put settings in the Server to send ETRN to and Parameters for ETRN boxes as your Internet provider has instructed you.