Server related issues
 - Use a domain name which is identified by a verifiable IP address. Make sure that if someone checks on the domain of your From address and Reply-To address that these addresses are valid, and the machine that would receive any Reply email can be identified.
 - Using SPF identification for your domain helps. It won’t flag you as a good guy directly, but it will prevent bad guys from successfully masquerading as you.
[Comments from Anurag: We did a research on this and feel this is not a good idea at the moment. It causes problems when people have alias accounts which forward to some other account]
 - abuse <at> and postmaster <at> addresses. Make sure you have active and monitored abuse <at> and postmaster <at> addresses. Register them with abuse.net
 - Yahoo Tip: Segregate your lists to different IP addresses. If you maintain several lists (or clients, especially for an ASP), you may want to segregate your lists to ensure that users are marking each list on its own merits. If user sees both spam and legitimate mail from the same IP, their notifications to us will be hazy and will likely result in the spam overiding the legitimate mail.
 - Yahoo Tip: Secure your mail servers. Open proxies, open relays, broken frommail scripts, and other insecure servers are frequently found by spammers. Make sure users are telling us about your mail, not someone abusing your system.
 - Yahoo Tip: Maintain accurate reverse-DNS information for your mail servers. Yahoo! Mail makes extensive DNS checks for each connection, and an accurate reverse DNS will ensure prompt processing of your connection and email.
Programming issue
 - Use an intelligent message id which ties correctly to your system. Use an intelligent mailing agent, one which identifies itself in the headers and which isn’t heavily used by spammers. Make sure your date header is correctly formatted and in the correct time zone.
 - Use email composition and mailing tools that work correctly. Well constructed emails (technically correct) can be readily identified as not-spam. Emails with missing mime sections, invalid or missing message-ids, invalid or missing date headers, subject or other headers with unescaped unicode, etc., are frequently signs of spam.
 - Avoid useless or needless encodings. Don’t use base-64 encoded text unless you need to.
 - Test your email with SpamAssassin. Send your draft to/through a system with SpamAssassin running, and see how it scores. If your email hits a number of high-scoring SA rules, then you can determine why and reduce your email’s score.
 - Your newsletter must be double opt-in / confirmed opt-in, and must not be a subject of spam complaints.
 - Yahoo Tip: Remove email addresses that bounce. Bounces are an indication that the mail could not be delivered because the user does not exist, no longer exists, or is unable to accept your email. List managers should remove addresses that generate bounces.
Email/Newsletter related issues
 - Accurate headers. Be accurate in who you are (From), and which systems the email goes through, preferably from your own servers, using your own domain name
 - Don’t include a disclaimer that your email isn’t spam. Don’t claim compliance with some legal criteria, especially one which is not actually law in your country. Only spam needs to claim compliance — non-spam is supposed to already be in compliance.
 - Use normal conversational language, be sure not to use excessive spacing and or capitalization on your subject. Don’t S.P.A.C.E out your words, don’t put str@nge |etters 0r characters into your emails.
 - Clean HTML. If you’re using HTML emails, use high quality HTML emails. Don’t use tools which generate horrendous HTML (example: MS Word). They often leave signs behind (like empty tags, eg: <B></B>) which are generally found in spam. Make sure your HTML is valid (run it through a decent validator). Unbalanced tags and invalid tags will also flag an email as spam. If you use a title, make sure the title is meaningful — the default titles generated by HTML tools are often used as spamsign.
 - Visible text. If you’re using HTML emails, do not use invisible text within those emails. Make sure your text colors and sizes are distinct enough and large enough to read. Invisible text is often identified as a sign of spam.
 - Email tracking (becons). If you’re using HTML emails, do not use invisible web-bugs to track your emails. If you must track your emails and whether they’re read, use visible graphics as part of your email, not invisible graphics.
 - Embed plain text email. If you’re using HTML emails, include a text part in the email as well, for recipients (and anti-spam checkers), and keep that text as close to the HTML copy as possible. The closer they’re related, the less likely your email will be seen as spam.
 - Avoid spamming words. Don’t include gratuitous references to spam subjects. Don’t talk about rolex watches, sexually oriented activities or drugs, or debt treatment, unless those topics directly relate to your email. And if they do, limit your email to one topic at a time. An email which mentions rolex watches, Viagra, porn, and debt all in one email will very possibly hit several rules that flag it as spam, even if everything else is clear.
 - Be careful where you advertise, and be careful which advertisements you carry. If you advertise with companies that send out spam, your domains will be flagged as being related to spam. If you carry advertisements for those who spam, your domains will be flagged as being related to spam.
 - Privacy policy. Make sure your privacy policy, including enforcement, and including query contact information, is easily found and clearly stated on your web site. It’s good to include this information (where to find this policy, contact information), in your emails. Again, people who need to find out whether you’re spammer will often look for that information.
 - Yahoo Tip: Send email to those that want it. We have found that using bought email lists is the quickest way to ensure that your email will be delivered to the bulk mail folder. Instead, use confirmed, opt-in email lists. To do this, after you receive a subscription request, send a confirmation email to that address which requires some affirmative action before that email address is added to the mailing list. Since only the true owner of that email address can respond, you will know that the true owner has truly intended to subscribe and that the address is valid. Without this process, you cannot be sure that the recipient requested your mail. Unintended recipients will likely tell us your message is spam.
 - Yahoo Tip: Honour the frequency of the list’s intent. If customers believe they are signing up for a list that will message them once a week, and they receive messages daily, they will likely mark messages as spam.
 - Yahoo Tip: Include valid unsubscribe links and periodically refresh your list. Unfortunately, spammers have taught users that unsubscribing is a bad idea. By periodically sending a confirmation email, you can be sure that the people receiving your email want to receive it.
 - Yahoo Tip: Honour unsubscribe requests as fast as you honour subscribe requests. When a user unsubscribes, they don’t want to receive that mail anymore. Promptly removing them from the list should help to prevent user marking messages received after unsubscribing as spam.