- Don't send unwanted bulk emails.
- Ensure that you're compliant with the CAN-SPAM act - make sure you provide a way to unsubscribing.
- Configure SPF, DKIM and DMARC records.
- Include a Text-Only version, except well-formed HTML.
- If an email address no longer exists, stop sending that address emails.
- Ask users to add your email address to their whitelist.
- Avoid phishing phrases and trigger words. Some common examples are "Click here", "Amazing", "Special promotion", and other.
- Avoid using all capitals in your subject and body unnecessarily.
- Avoid using punctuation in the subject.
- Do not attach any files to email that could be classified as suspicious.
- Don't use false or misleading header information. Your "From", "To," "Reply-To", and routing information – including the originating domain name and email address – must be accurate and identify the person or business who initiated the message.
- Don't buy subscribers. If you're buying email lists and sending content to people who never signed up to receive them, there is even a greater chance you'll be heading for the spam folder.
- Ensure that your internet IP address assigned to you by your Internet Service Provider is not listed on a spam blacklist (Spamhaus, etc.).
- Limit your sending frequency.
- Avoid using excessive punctuation in the body of email, eg. punctuation!!??
- Avoid substituting letters with numbers, eg. "w3b h0sting".
- Avoid having gaps between the letters in words, eg. "l e t t e r s".
- Avoid using many different font colours in your email.
- Avoid using large font sizes.
- Avoid using gimmicky words or phrases that are commonly found in spam emails, eg: "Click Here", "Buy Now", "As Seen On", "Money Making", "Get Paid", "Make Cash", "Pre-Approved", "Hot Deal", "Satisfaction Guaranteed", "Lowest Prices", "Save Big", etc.
- Maintain a good text to image ratio, ie. for every image include at least two lines of text.
- Avoid using shortened URLs (web links) in your email body, eg. bit.ly or goo.gl.
- Avoid adding a large number of URLs (web links) to the email body.
- Avoid using rude language or poor spelling.
SPF, DKIM and DMARC are three technologies that help to prevent your emails from getting into spam. All three are DNS records that are added to the name servers.
- SPF is the list of servers, that are allowed to send emails using your domain name.
- DKIM adds a digital signature to the outgoing message, that allows the recipient to check if sender was indeed authorized to send email using particular domain.
- DMARC verifies, that SPF and/or DKIM are in use and allows to order reports on frauds and emails that are not legitimate/compliant with the rules.
