- SMTP gateway servers use memory primarily for maintaining connections and keeping track of vital information about messages in the queues.
- The memory used to store message properties on queued e-mail can be significant.
- SMTP stores messages in the queue in two states:
1. opened (that it, it keeps a handle open) or
2. closed (that is, it closes the handle).
- The maximum number of messages that an SMTP gateway queues before refusing new messages is 90,000.
- SMTP can keep 1,000 messages in the queue open at any particular time, closing old messages as new ones arrive.
- An open message in the queue consumes approximately 10 KB of memory in the Inetinfo process, and a closed message consumes approximately 4 KB of memory in the Inetinfo process.
- The maximum number of messages that an SMTP gateway queues before refusing new messages is 90,000.
- A simple calculation that explains this,
1,000 open messages = 10 MB of Inetinfo memory
1,000 open messages + 20,000 closed messages = 80 MB of Inetinfo memory
1,000 open messages + 89,000 closed messages = 366 MB of Inetinfo memory
Traffics:
- Low-traffic SMTP gateway servers can perform adequately with 256 MB of RAM.
- In high-traffic data centers, where large queues are common and large distribution lists are expanded, at least 512 MB of RAM is preferred.
- Generally, an SMTP gateway server does not benefit by having more than 1 GB of memory.
Which means that at any given point of time, any Exchange server with basic configuration is capable of handling emails of any size.
