SMTP and Exchange Server 2003.
I’m going to start with something simple, but its something I find that many administrators often get confused about, “message flow” especially in Exchange. Later I’ll pass on some tips on troubleshooting message flow but for now lets have a look at SMTP the core fundamentals of messaging. Without SMTP nothing will happen and i want to explain the connection between SMTP and exchange. For the record my reference in this post is against Exchange Server 2003.
Lets start at the configuration side of things:
Before you set up your Exchange server to send/receive mail, you should understand how SMTP (Simple Mail Transfer Protocol ) enables messages to flow. Exchange uses SMTP to deliver mail both internally and externally. If you hadn’t guessed SMTP is the standard throughout the internet for moving mail and if you are really keen check out RFC 2821 and 2822 for really detailed stuff on SMTP.
Windows SMTP is a component of Internet Information Services. Exchange server needs the SMTP service as its native transport protocol, so if you hadn’t guessed Exchange uses SMTP to move all mail both internal and externally. BUT when Exchange server is installed it extends the SMTP functionality and here’s how. The management of the SMTP service is moved from IIS console to ESM (Exchange System Manager) This is done by means of virtual servers.
It also implements support for link state information. Link state is used to determine the best way for sending messages between servers. This is based on connectivity, current status and of course cost. It also looks at your topology and associated expense based on route, pretty good hey?
There’s more -
Setting up an Exchange Installable File System (IFS) store driver to allow message retrieval from and delivery to the Exchange store.
Setting the disk location where messages are queued
Implementing support for advanced queuing.
Enhancing message categorization
There’s also some extended support to command verbs (used for link state routing and other Exchange functions)
I think the other thing to remember as well is the connection Exchange has with Active Directory and the IIS metabase. With ESM any changes made are written to AD allowing for easy administration
Recap: SMTP is part of IIS, Exchange extends its functionalility.
SMTP virtual servers are the Exchange mechanisms for controlling/managing SMTP. Each virtual server represents an instance of the SMTP service running on Exchange, remember this when creating several as it will effect performance. Microsoft say its a common misunderstanding that many SMTP virtual servers increase throughput, they don’t I’ve tried it, one instance is enough.
In the next part we’ll talk about sending and receiving emails, whats required for this to work?