Avoid Being Flagged As Spam

An important feature of all the email you send is to make sure that you have an opt-out link at the bottom so that any people wishing to un-subscribe.  This is a simple yet very powerful gesture as your email recipients will understand that you are a professional business and you highly consider your relationship with your readers.  If a reader clicks on this then their email should instantly be removed from your mailing list and if you use one of the big companies like Aweber then this is normal.

Frequency Of Email

It is never a good idea to just keep bombarding your mailing list with email after email trying to sell them something. This is the quickest way to get someone to unsubscribe from your list. Depending on the niche you are you should email them occasionally and not all the time and only when you have something worthwhile to say or recommend.

Provide Good Content

It is always beneficial to provide your mailing list with quality content and you will build up a trust so when you do actually recommend a product then there will be more chance of them buying it.  It is recommenced that you should send a product review or guide every 3 to 4 email .

Use A Reputable Company

If you use a reputable company like Aweber or Getresponse then you will get high reliability and it will all be managed for you for a small monthly fee.

Overall there can be a lot of money to be made by building up your email list and selling to them.  As long as you provide quality content in the email and occasionally recommend a good product you will do well.