Spam is defined as email that is sent to a large number of recipients, where the recipients have not explicitly given permission to be emailed and the purpose of the email is to solicit a commercial action, eg. selling a product.
Mail servers use spam filters to in an attempt to prevent spam from reaching the intended mailboxes. These Spam filters use a variety of filtering techniques to attempt to accurately determine whether an email is a spam or not. Many of these spam filter ‘rules’ are based on words or characters that are commonly used in spam.
These techniques are dynamic and adapted on a regular basis as spam emails evolve in nature and content in an attempt to fool and bypass these filters. For this reason, there is no complete list of rules to guarantee that your email will pass spam checks. There are, however, some best practices you can follow to lessen the chance of your email inadvertently being classified as spam.
- Avoid using all capitals in your subject and body unnecessarily.
- Avoid using punctuation in the subject.
- Avoid using excessive punctuation in the body, 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.
- Include a text version of your email if you are sending an email in HTML format.
- Maintain a good text to image ratio, ie. for every image include at least two lines of text.
- Ensure that your internet IP address assigned to you by your Internet Service Provider is not listed on a spam blacklist.
- Add an accurate SPF or DKIM DNS record to your domain.
- 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.
Even if you do follow the above best practices, there may still be a chance that an email you have sent ends up in the recipient’s junk or spam folder. Spam filter administrators do not publicise their filtering techniques in a bid to stop spammers from circumventing spam filtering.
It is therefore advisable that if you do not receive a response within the expected time frame to follow up with the recipient via alternate means to confirm receipt of your email.