Internet Message Access Protocol version 4 (IMAP4) allows a
client to access messages in private and public folders on a
server. Users with an IMAP4 client can access mail in their
Microsoft Exchange 2000 Server mailbox without downloading the
entire mailbox to a specific computer.
A single client can access multiple mailboxes to retrieve
specific messages or portions of a message, such as an attachment.
IMAP4 clients can also search a mailbox and store flags to identify
messages that have been read. IMAP4 does not send mail. This
functionality is handled by Simple Mail Transfer Protocol (SMTP).
You can configure your IMAP4 server to grant
or deny access to specific computers, groups of computers, or
domains. You can grant or deny access to a single computer based on
an IP address or by overriding IMAP access on a per-user basis. A
group of computers can be either denied or granted access based
upon their subnet address and subnet mask. You can also control
access to an entire domain at once by specifying a domain name.
Both IMAP and Post Office Protocol (POP) are
internet messaging protocols that allow clients to access their
mail. The difference between these protocols is where the client
manipulates their messages. IMAP allows a client to access and
manage mail on a server. POP allows a client to download mail from
their Inbox on a server to the client computer where messages are
You can manage the Internet access protocols
on a separate server from the one on which the store runs by
deploying a front-end/back-end configuration. Essentially, a bank
of protocol servers can handle the incoming client connections
while the store servers are dedicated to running the databases. The
main benefits of a front-end/back-end configuration are a unified
namespace and a reduction of overhead for SSL encryption.