An impression in most of the cases cannot be created by one attempt. Here consistency is the key. If you are not consistent you will fail to make your mark in the mind of the customer. Here a threat of being a spammer is most prevalent but if you are using legitimate options you can overcome it. So work hard to keep yourself regular as doing so almost always leads to a greater number of sales.
Another way to extend the clicks on your email beyond its shelf life is to prompt your audience to forward the offer. The folks at Litmus found that the most forwarded emails were 13X more likely than the typical email to include “Share With Your Network” calls-to-action. By including forward-to-a-friend (or social sharing links, as we discussed above), you put it in recipients' minds to share.