How to Avoid Spam Filters

Spam emails are a part of life that we’ve all had to accept. Often generated by bots and sent in bulk, spam and phishing emails are constantly sent in an effort to outsmart email users, ISPs and ESPs. Some spam can be quite clever in the way that it presents itself, but there are patterns you can pick up on if you’re savvy enough.

Words to Avoid

Certain words in a subject line will often trigger spam filters, so it is important that you know what they are. You don’t want your contacts to mistake you for a spammer or phisher, do you?


The word “invoice” is used by many phishing emails. If you ever see this word in a subject line, there’s a chance that someone is trying bait you in. Always check the sender address to verify if the email is valid before doing anything. Don’t let a scammer profit from your carelessness.

PayPal, Visa, Mastercard or any bank/building society name

Any legitimate financial institution will never send you an email asking for you to verify your account details or ask you for personal information. Scammers will often send emails with the same color scheme and layout as an official financial email, where they will redirect you to a mirrored site, made to look like the one it is spoofing. A good rule is to simply delete these emails as it simply isn’t worth the risk.

Gift/prize draw/lottery/Specially for you/Winner

These types of emails always appear in users’ inboxes. Hundreds of thousands of emails are sent to people with a subject line stating that they have won a big prize or that they have been entered into a sweepstake they’ve never entered before. It is surprising how many fall for these emails, yet scammers continue to send these by the millions every day.

Urgent/Please help

This is where phishers pretend to be an affluent person in a foreign country who have had to flee from some supposed danger. You will have been chosen as the sole trustee of their money and they promise that they will give you a great reward for helping them open an account to transfer the funds to. You’ve probably heard of the Nigerian scam and you have probably seen them yourself.

Casino/Free Bets/Deposit bonus

A gambling scam email will promise high returns, free entry or double deposits. Unless you recognize the website it is advertising, delete the email immediately and do not click on any links.

Other Tips

So now you know which words to avoid in the subject heading or text, but is there anything else you can do? Here are some tips that may surprise some of you:

Font size

Check that you are using a normal size font. If the text is too small or too large, it might alert spam filters. The email needs to look as normal as possible simply because spam filters have gotten wise to previous spamming techniques. This also means don’t use all CAPITAL LETTERS anywhere in your email or subject line.

Your spelling

We say this often, but you have to proofread your messages before you send them. This is not just for professional reasons, but because spam filters pay attention to anything that you wouldn’t normally see in an average person’s email. If there is a lot of repetition, too many spelling mistakes and gaps in words, it will be noticed. Spam filters are also looking for too many underlined words, loads of exclamation points and different colored fonts.

Image and text ratios

Emails can appear suspicious if the link-to-text or image-to-text ratio is too high. Spam filters can’t read images, so many spammers use the tactic of displaying the majority of their offers in text or links. It is important to have appropriate links, but think about how these need to appear in the text and don’t include too many. Also, remember to add alt text to all images so that they can be easily read by all email clients.

Don’t be illegal

The CAN-SPAM Act was passed in 2003 and sets the rules for commercial emails. Make sure your emails comply in the following ways:

  • Don’t create deceptive content – never lie in your header, subject lines, reply to addresses, call to actions or from-names.
  • Make unsubscribing easy – always have an unsubscribe link, which stays live for at least 30 days after sending.
  • Include your real mailing address – you must include your actual physical posting address in your email.
  • Always have consent – never send any emails without getting the express permission of the recipient.

If you are emailing to Canada, you also have to be aware of the Canadian Anti-Spam Law (CASL). For more information, visit our dedicated website.

Use online tools

There are online tools that you can use to test your marketing emails before you send them. A simple Google search will point you in the direction of numerous free spam testing tools that will save you a lot of problems.


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