Include a real name, not just an email address in the "Sender Name" field.
Make sure it is clear who your email is from i.e. the “Sender Name” should be familiar to email recipients.
Use only verified sender addresses.
If its a regularly scheduled newsletter, include the date or month of the issue (August 2011) and "newsletter", "news", "list", or the frequency (daily, weekly, monthly).
Avoid words which sounds like spam and phrases like Opportunity, Money Back, Incredible, Targeted, Offer, You Have Won "$ followed by numbers" and similar such phrases.
ALL CAPS in your subject.
Usage of extra white space in your subject.
Using special characters in your campaign subject.
Using a sender address that ends with a number.
Avoid using the email content or subject line related information in "Sender Name".
Use a white background.
Send only relevant information to your customers.
The subject of your newsletter and title should relate to each other.
Use only licensed images.
Use in-line style (CSS) for your newsletters.
Greet your customers with their names - First Name/Last Name.
Make sure there is more of text used and maintain a good ratio of text to image area.
Usage of "Dear User or Customer" to greet your recipients.
Claim your message isn't Spam - This could actually end up with a lot of Spam complaints.
Using "Click Here" links.
Using "Untitled" in title tags.
Include thick borders in your campaign content.
Using scripts such as Java scripts.
Using colored background.
Using invisible text.
Repeatedly sending the same email/campaign to your subscribers.
Using URLs such as www.campaign.zoho.com since our email tracker module will replace all your links with tracker URLs such as www.zohocampaign.com/tracker? prior to sending. So, your links might end up having a mismatch in domain names present in the inner text and its target (HREF), which one of the anti-spam rules to mark an email Spam.
Maintain a low ratio of text to image area. Especially, image-only emails, which is currently the top tactic employed by spammers to get past filters.