Email servers are the intermediaries that help you send messages to other people. Client programs read and write those messages: examples include Eudora, Emailer, Netscape Messenger, and Microsoft Outlook. The WebSTAR Mail server supports SMTP, so it can communicate with other servers that support the same Internet standard, such as Sendmail on Unix, Microsoft Exchange on Windows NT, and Eudora Internet Mail Server (EIMS) on the Mac.
WebSTAR Mail is a standard SMTP (Simple Mail Transfer Protocol) server. This means that it participates as a peer of all other Internet SMTP mail servers, sending messages via the most direct route available to the recipients' mail servers, and receiving messages from other servers. SMTP servers do not "log in" to retrieve messages, they simply wait for messages to come to them.
To send a message using the WebSTAR Mail server, a user creates it in their email client, which transfers the message to the server. WebSTAR Mail then looks up the IP address of the recipient's mail host and sends the message to that server. In some cases, other servers are authorized to accept and forward email messages--this is all directed by DNS and routing configurations.
Assuming all is well, the message and any attachments are sent right away. If the receiving server is temporarily unavailable, the sending server will queue (store) it and try again later. If there is another problem, such as a mistake in the email address, the receiving server may bounce (reject) the message. WebSTAR Mail will then pass that bounced message back to the original sender.
For technical details on SMTP, see RFC 822 . For enclosure processing, see RFCs 1652 and 2045-2049 .
WebSTAR Mail supports POP version 3 For technical details, see RFCs 1939 and 2195 .
POP stands for "Post Office Protocol", which allows email client programs (also known as POP clients ) to log in and download messages from the mail server. The user then reads the messages and replies, and the email program uses the SMTP protocol to send the messages back out through the server.
Many POP clients allow users to specify if the messages should be retained on the server or deleted right away. The only reason to retain messages is if the user is accessing the mail account from more than one place and wants to read their email at all their computers. IMAP (described IMAP ) is a better solution for this problem than POP.
All WebSTAR Mail accounts are accessible via POP clients. You can set the message size limit, forwarding, total storage, and APOP security options. See POP Connections and Users & Accounts Settings for more details.
Standard POP passwords are not encrypted. This means that anyone who is between the client and the server can intercept the login command and capture the password. They could then use that password to send messages from accounts on your server, without anyone's knowledge. This can be used for unwanted email, threats and other undesirable activity. For this reason, we recommend using APOP whenever possible (see APOP ).
The following are examples of POP compatible mail clients:
WebSTAR Mail supports APOP --Authenticated Post Office Protocol--which uses a secret passphrase system to identify each client for security. However, some older email programs do not support APOP, so you can set this option for each individual account.
For technical details about APOP, see RFC1734 .
IMAP --the Internet Mail Access Protocol--allows users to read their mail on the server and only download messages and attachments to a local machine when appropriate. Its main advantage is that the user can see all the message headers at a glance, and open only those which are interesting. This saves significant download time, especially if users often forward or delete messages without reading them.
For information on IMAP, see the IMAP Connection at www.imap.org . For technical details, see RFC 1203 and 2060 .
IMAP demands on the server disk can be significant, as messages are often left on the server, rather than stored on many client machines.
WebSTAR Mail supports IMAP clients with settings for message size limit, forwarding, and total storage limits. In addition, you can specify for each account whether IMAP clients can create, rename or delete mailboxes on the server.
WebSTAR Mail supports IMAP version 4 revision 1. The following are examples of IMAP compatible mail clients:
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Netscape Messenger, and Communicator Mail Module (Mac and Windows) |
WebSTAR Mail is also accessible from any browser, so your users can read mail from shared computers, while travelling, and so on. For more information, see Email Access from Web Browsers
LDAP (Lightweight Directory Access Protocol) allows people to look up names and email addresses in your company listings. This is particularly useful for Intranets and distributed corporations, so users can find addresses for other employees quickly and efficiently. It is like a company phonebook for email addresses.
For information on LDAP, see www.umich.edu/~dirsvcs/ldap/index.html . For technical details, see RFC 2251 .
Users may have to add your WebSTAR Mail LDAP server to their list of directory servers. They don't need to worry about logging in or root servers. All they need to do is enter the name of the WebSTAR Mail server host into the Directory field, and they will be able to search for all the user names and email addresses local to that server (including groups and forwarding addresses).
You should restrict access to your LDAP server, so that only people in your organization can find these addresses. Otherwise, they could easily be harvested by spammers. For restrictions, see Protect Your User Directory and Restricting Access to LDAP .
Some firewalls may restrict access to your LDAP server on port 389. You may need to talk to your Network Administrator or ISP about opening a hole in the firewall if you want access from outside.
LDAP is an Internet Standard and all LDAP clients should be able to see the WebSTAR LDAP server. The following are examples of LDAP compatible clients: