The first is correct but annoying; the second is a ball-park guess.
For some reason, people tend to prefer the second.
Answer 1: "It Depends"
(Told you it was an annoying answer.)
The thing is, it depends on who you are sending your newsletter to.
Here's an example of two newsletters. One is about the birth of your first daughter and it is being sent to family and close friends. The other is about Viagra and it's being sent to a bunch of names harvested from the internet.
Everyone will open the first email; almost nobody will open the second.
The reason, of course, is the relationship you have with your list.
Most businesses will be somewhere in between.
If, for example, you are communicating with past clients who recently enjoyed working with you, it's likely you will have a high open rate because they already have a strong relationship with you centered on a shared interest. If you are communicating with a list of leads bought from a third-party vendor, your open rate will be much lower. They don't know who the heck you are.
Of course, the ideal situation is to have such a strong relationship with your clients and prospects that they look forward to hearing from you. To do that you:
- Communicate only with people who have asked to receive information from you
- Constantly provide value in your newsletters
- Continue to communicate over the long term, to build a trusted relationship
Answer 2: Between 20% and 30%
That's the ballpark figure.
But really... it depends.
[Picture by svilen001]