This is also known as ad-swapping. List your email newsletter in mailing list and newsletter directories. Let your readers know they can forward their issue on to their friends, so long as they keep the issue intact, including all the copyright information. Encourage this activity. If you have a marketing budget for your newsletter, then take out some online ads.
Online advertising is an effective way to grow traffic more quickly.
Try a variety of ads, including advertising in other newsletters, banner ads and classified ads. Put a short description and website link to your newsletter's webpage in the signature line of your email. This way you will promote yourself through your emails. However, be sure not to spam newsgroups or send unsolicited emails about your newsletter. This can generate complaints, ill-will and damage your brand name.