Here are some benchmarks to use as a guide when setting KPI goals for e-mail newsletters or alerts. The open rate and the bounce rates are the most important.
The benchmarks come from a study by a e-mail vendor featured in an eMarketer story.
| Metric | Low | High |
|---|---|---|
| Open rate | 20% | 31% |
| Click rate | 4% | 7% |
| Soft bounce rate | .1% | 2% |
| Hard bounce rate | .3% | 3% |
| Unsubscribe rate | .4% | .5% |
The open rate is the most important; the total number of subscribers much less so. You’re not engaging your audiences if you’re pushing e-mails to them but they’re deleting them without even looking at them.
If the content in your newsletter is pretty complete in itself (e.g., breaking news alerts, news briefs), your click-through rate will be low. You might not even want to monitor it.
Not all e-mail newsletters should relentlessly focus on pushing traffic to sites. Segment your audiences and ask each segment how they would most like to get your content. Perhaps an audience largely gets its e-mails via a smartphone, and don’t want to link to a site.
A little bit of engagement – subscribing to and regularly reading your e-mails – is better than none at all.
Hard bounce: The number of e-mails returned due to invalid e-mail addresses or spam filters.
Soft bounce: The number of e-mails returned due to temporary reasons such as inboxes being too full or the subscribers’ e-mail services being down.
News Numbers 
Here are a few actual email marketing benchmarks to throw into the mix: http://emailcritic.com/2009/09/29/how-does-your-email-marketing-program-stack-up/