Here are some guidelines for email marketing metrics with respect to prospect-development types of emails targeting IT professionals.  If your campaign falls into this range, you are meeting industry standards.

Unique open rate: 10 to 20% after 3 blasts
Click-thru rate:  2 to 5% (based on the unique open rate)

It’s important to keep these metrics in mind when evaluating your campaign.

Also, conversions on click-thrus can vary.  Maybe you are running an event or webinar, in which case 33% to 50% conversion on click-thrus can be expected.  So plan your starting list accordingly.  A list of 10,000 contacts (assuming it is very clean) with a strong performing email will generate 2000 opens, and 100 click-thrus.  So anywhere from 30 to 50 registrants from email alone can be expected from the campaign.  This is a best case scenario assumption on opens and clicks.