SMTP Service Authentication
The SMTP service listens for incoming connections on port 25 (or any other specified ports), and having checked that it shouldn't be rejecting it, sends the mail to Mailtraq's mail routers, which will either place it in local mailboxes, or send it out to remote recipients.
KB05111702 Allowing controlled Relaying (Configuration advice)
Typically you offer an SMTP service that doesn't require authentication on port 25, and optionally an SMTP service that does require authentication on port 587.
Typically mail coming from outside the local network, addressed to local users, will be received through an un-authenticated connection. This simply means that the sender doesn't have a username and password on this system.
Mail from local senders can also be un-authenticated. If the connection is coming from an IP address within the LAN it can normally be accepted, and safe to relay to external recipients. Read about LAN definition ...
If your users are connecting from outside the LAN (say from home), and they are not using a VPN, their IP address will be external, and Mailtraq would not normally allow them to send mail through the system to external recipients. To do so would make the system an Open Relay.
To allow your users to send external mail, without becoming an Open Relay, they need to authenticate. There are three methods supported by Mailtraq. The choice of method is normally determined by the options available in the client software. Whatever the method of authentication, the system requires the username and password of the individual Mailtraq users (as specified in the Options | Users dialog).
This is the most secure method of authentication, involving an encrypted password.
This works in the same way, but the passwords are sent in clear text.
This works by piggy-backing on the authentication performed by the POP3 service, whitelisting the IP address the POP3 or IMAP collection was authenticated on, for a limited time.