Email Protocols

Talk about a lot of questions...
First, have a look at http://www.zdnet.com/pcmag/pctech/content/14/21/ig1421.004.html
This is a good description of IMAP. The key thing to know about it is that email stays on the server and does not get stored on the client. This is good because you can back up the server.
When you use Personal Folders in Outlook, you only connect to the server a) when the server notifies (via UDP) the client that there is new mail or b) at pre-scheduled intervals. BUT - youdo have to download all of your mail to the local machine. IMAP is more like when you do not use Personal Folders (PSTs) on an Exchange server.

So either Exchange without PSTs or IMAP should use the least bandwidth, but requires more server space. Exchange with PSTs will use the most bandwidth. Exchange with OSTs is a very good compromise that gives you speed, reliability, and security. See http://www.microsoft.com/technet/treeview/default.asp?url=/TechNet/prodtechnol/exchange/maintain/optimize/optimsg.asp for a good whitepaper on this.

Maybe I am alittle confused, but it would seem to me if I were to use IMAP or Exchange without PSTs, that they maintain a constant connection with the exchange server. If I use Exchange with PSTs, they only make a connection with sending/receiving. When we are talking about around 100 users connecting to an exchange server over our WAN (T1), how does the IMAP use less bandwidth. It would seem to me that using IMAP or Exchange without PSTs would use up more bandwidth because you are constantly connected to the exchange server. Please correct me if I am wrong.

Woody

This question was closed by the author

When you use exchange, unless you deliberately set it up for remote, you will maintain a connection between each client and the server. There is not a lot of traffic associated with this connection, but there is a bit. This buys you immediate notification when a new email comes in.

If you are in remote mode, you connect to the server and ask for mail either on a schedule (e.g., every 10 minutes) or on demand, when the user hits Send/Receive. Your poll can be using the exchange server protocol, IMAP, or POP3. You can choose to use dial-up or network for this connection.

In general, I believe that you actually get better bandwidth utilization with the continuous connection, particularly if you are keeping mail on the server rather thandownloading mail to a .pst. The reasons are:

a) If you keep mail on the server, the client must cycle through all old mail to find out if you have new mail.

b) If you use an exchange connection, attachments are not loaded to the client until they are to be read. If you have people who routinely send lots of copies of large presentations or spreadsheets to people who rarely read them, you avoid the download traffic.

Note that if you are really seeing too much traffic on your T1, and that T1 is between you and another office you might do better to install a second Exchange server at the remote end. That way all users are talking to a local exchange server, and inter-site traffic only moves over the T1 once.

Good luck.