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In House list:
The list of email addresses an company develops on its own. Email campaigns based on in-house lists are invariably more successful than those based on purchased or vendor lists. It is always the recommendation that a business should develop its own in-house list.

IP address:
A unique routing address assigned to each device connected to the Internet. An IP address can be dynamic, meaning it changes each time an email message or campaign goes out, or it can be static, meaning it does not change. Static IP addresses are best, because dynamic IP addresses often trigger spam filters or bans from search engines.

IMAP:
Internet Message Access Protocol, a standard protocol for accessing email from a server.

Inventory:
Inventory is the term commonly used for the subscriber base or size of a an email or newsletter list.

ISP:
Internet Service Provider. Examples are BT, AOL, Wanadoo, Freeserve.