using VB as a server is so simple using Winsock ..
all the problem in the commands used to send emails and to read the incoming ones ..
this information may be helpful ..
** How email servers works ?
** Answer :
The first component on an e-mail server is a list of user accounts. The other major component in a simple mail server is text files. Each account has an associated text file. These text files are what composed messages are stored in.
The server also has to know how to communicate with other e-mail servers. If it can't communicate with them or can't locate them, no e-mails can be sent or received. This is where the concept of domains and DNS servers comes in.
Domains and DNS Servers
A domain is a system or collection of systems that share a common database identified by a name. Domain names are how computers and servers locate each other.
A DNS server is a specialised device that keeps lists of the associations between domains and IP addresses. It distributes that information to other DNS servers on a hierarchical basis, and responds to queries regarding the location of other domains.
There are different types of e-mail systems: one for sending e-mail and two for receiving e-mail. The sending e-mail system is SMTP (Simple Mail Transfer Protocol). There are two different types of receiving e-mail systems: POP3 (Post Office Protocol version 3) and IMAP (Internet Mail Access Protocol).
When an e-mail is delivered to the recipient's domain, it's received by their SMTP server and routed to the POP3 server. POP3 reads the first part of the TO: field and matches it with the account name and text file for the recipient.
The message then waits in the queue until the recipient calls for his e-mails by either opening the e-mail client program or by clicking Send/Receive. At this point, the entire text file is downloaded to the recipient's hard drive, parsed by the e-mail client software and then displayed as a set of messages.
An IMAP server is similar to a POP3 server. However, in the case of an IMAP e-mail server system, when the recipient clicks on e-mail, they're not actually downloaded onto the hard drive. Instead, the e-mail client opens the e-mails and allows the user to read them while they are still on the server.
Messages appear in Outlook just as if they had been downloaded. All the folders that come by default, such as Inbox, Sent, Drafts, and Outbox, actually exist on the server along with personal folders. The IMAP server is typical in business environments. Because all the e-mails remain on the e-mail server, they can be backed up, just like any other server data.
E-mail is the indispensable communication system of 21st century commerce. Your ability to control the flow of e-mail into and out of your company is as necessary as your ability to control telephone traffic. Therefore, it's critical for the e-mail server to be backed up regularly and frequently and this is done easily with an internal server system.
** I'm searching in this topic now may find more info. because i need it too ..