The two types of E mails that people are guaranteed to open are 

1)                  If they know the sender

2)                  If the subject line is of interest or benefit

When doing e-mail promotions, the chances are the recipient will not know you on a personnel level, so your subject line can literally make or break your success a critical point that the majority of marketers miss.

Think about all of those e-mails you're probably getting on a daily basis with subjects like:

"MAKE £75,000 EVERY WEEK GUARANTEED!"
"Follow my plan and never work again!!!!"

Do you open these e-mails? Because I know I don't! The subject line makes it obvious that the e-mail is spam. That it's from someone you don't know... or it doesn't offer a clear benefit that makes you want to read it.

Now let me ask you a question: How many of your legitimate newsletters and opt in e-mails are mistakenly deleted by your subscribers who read your subject lines and assume it must be spam!

When you write your subject lines, you basically have 3 choices:

1)         You can make an announcement or give news (e.g.,"ISS shows members how to write white papers").
2)         You can make the reader curious (e.g., "ISS gives members a definitive guide on Google ad words").
3)         You can emphasize how the reader will benefit from opening your e-mail (e.g., Discover tips for writing subject lines that will increase your sales).

Out of these 3 techniques, you will always be most successful if you write subject lines that state a clear benefit and tell the reader exactly how they are going to save money, save time, make their life easier, etc., by opening and reading your e-mail.

If you can state a benefit AND create curiosity (e.g., Discover this proven marketing strategy that will increase your sales!), so much the better!

But again, the key when writing subject lines is to emphasize benefits by considering your product or service from your customers' point of view...

How will they benefit from taking the time to read your e-mail?

What will they learn?

Is your product/service going to save them time?

Is it going to save them money?

Or is it going to improve their lives in some way?

Write subject lines that emphasize these benefits and I guarantee that you'll dramatically increase the number of subscribers who open and read your e-mail.