Old-line retailers—desperate for sales—were criticized last month for deluging holiday shoppers with irrelevant emails.

Are you guilty of acting desperately, too?

Many event marketers are swamping attendees’ in-boxes with vague offers of “must-attend” trade shows and conferences.

Attendees are growing angrier and more resistant by the day.

How can you tell you’re sending too much email?

Your opt-out rate.

If you see it start to climb abnormally, you can bet you’re sending subscribers too many emails.

One easy way to prevent opt-outs is personalization.

Personalization counteracts the impression you’re “spamming” subscribers.

Personalization also boosts response. Simply including the reader’s name in the Subject line boosts open rates over 25%.