Sending mailing to your customers and/or visitors is often an important way to bring additionnal revenues for your company. Regulary sending emails (between one week and one month between each batch) is important so people don’t forget about you and know about your latest offers. Add some discounts and stuff in the mail to ensure people will have a good reason to read them, and you’re done.
Now the question is “who should receive your mailing”. People usually thing it’s OK to just buy an email address database and send them ads everyday to let them know about you, and your offers they all really need. This is most likely going to result into your company name becoming a keyword to detect spam, which is probably not what you are expecting.
Even if you let them a choice to “opt out” from your mailing, most people will not optout in fear this will just reveal their email is valid and read, and trigger more spam. So your list will be full of people who will not opt out, but instead click “report as spam” button. This is most likely not what you want.
Now, you know you can only send mailings to people who have subscribed of their own will on your website. “Their own will” cannot be verified simply. As far as I am concerned, there are two solutions. For a visitor you have to send an email notifying him he asked to subscribe to your list, and that he must click some link to actually receive it. Including a link to privacy policies can be a good idea too.
Next comes real customers, people who have actually bought on your site and asked to receive your mailing (not with a pre-accepted subscription). For them, as they are more likely to trust your “optout” link, you can probably skip the double optin step.
Don’t forget that you also need to send mails from times to times. One full month without mail is a no-go, as customers will have forgotten about you and their subscriptions, and will immediatly suspect spam.
Sending mailings is an important communication job, and you need to have news and stuff to put in your mailing. Make it interesting for your subscribers, and send mailing regulary (every two weeks sounds like a good idea). If you can’t include a “new cool products” part, try to include news from other activies from your company or special offers. Sending the same newsletter everytime is a no-go.
Anyway remember that spam (any unwanted email, even if it’s unwanted because the subscriber forgot he was subscribed) is not good for your subscribers, not good for your image, and not good for Internet as a whole.