Six email tips to avoid spam filters

Posted October 4, 2017

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By Chelsey Feldman

Product Marketing at Outreach

Spam is never a word you want to hear. At best, it means you’ve just eaten mystery meat, and at worst, it means your email isn’t being read by the people who need to see it.

Spam filters look for certain criteria to determine if your email makes it through to a coveted spot in the inbox. They weigh each factor and add them up to assign a spam score. If the score exceeds a certain threshold, your email will get flagged as spam and go straight to the junk folder. Each spam filter functions a bit differently, though, and “passing” scores are typically determined by individual server administrators. This means that an email could pass through Spam Filter A without issue, but get flagged by Spam Filter B.

With such an arbitrary seeming spam scoring system, how can you be sure your email won’t end up in someone’s spam folder? Well, you can’t. But there are a few tips to avoid spam filters that you can follow to make your emails more likely to land in your prospect’s inbox, and it wouldn't hurt to try Outreach's sales email tracking features and other sales email tips.

1. Link wisely

Links are really misunderstood when it comes to emails. They’re important for you to include, but they’re usually one of the first things to set off spam triggers if you use them wrong. For one, don’t include too many links. You should have a good link to text ratio as an email full of links will set off the spam alarms.

Additionally, be careful what links you’re including. Every link has a domain reputation, and you want to be sure you’re in control of the reputation of the links you’re sending. A feature like Branded URLs gives you more control over your email links by allowing you to white label them with your own domain, reducing the risk your links will cause your email to be flagged by spam filters.

2. Practice safe sends

Just like it’s important to use links with reputable domains, the reputation of your IP address and sender domain is equally important. Make sure you’re not sending from a domain that has been previously been flagged for spam. You can check if your domain is on the email blacklist at Sender Score.

After you’ve ensured your domain isn’t on the blacklist, set up some best practices to keep you in the clear. For one, avoid sending more than 5 emails to the same domain (like sending a bulk email to 100 customers at the same company) so you don’t risk getting blocked across the domain.

Also, be sure to maintain a low bounce rate – the more bounces, you get, the less reliable your domain looks because you appear to be sending to unreliable lists. Services like Kickbox ensure you only send email to real users and help you weed out the low-quality contacts from high-value ones. Additionally, you can use a platform with built in limits and safeguards that block mail from being sent after receiving too many bounces to protect your own domain reputation.


We’ve all seen that awful email – you know, the one with crazy formatting that screams “READ ME I’M A SCAM!!!!!!1” You’re not sending a scam but sometimes it’s easy to get overly excited in your subject line and give off the wrong impression – both to spam filters or to recipients who might see your email. Here are a few things you should avoid at all costs:

  • Using too many exclamation points!!!!!!!
  • Including spam trigger words and phishing phrases (WIN, Free!, etc.)
  • Forgetting to use spell check

When in doubt, use a service like to gauge the likelihood of your email being flagged by spam filters.

4. Remember text etiquette

There are a few text best practices that will help your email look more legit. For one, don’t use red or white text. This is a common format that spammers use, so it’s an instant red flag for spam filters. Also, if you’re sending a newsletter or anything with fancy HTML, always include a text only version of your email.

5. Don’t embed crazy things

There are a few best practices to bear in mind when you level up and start embedding things into your email. When it comes to images, they’re ok, but make sure you have a solid image to text ratio in your email. Using one large image as your entire email, or too many images in general, tends to end up in recipients’ spam folders.

Beyond images, a good rule of thumb is “just don’t.” Don’t Use video, Flash, or JavaScript within your email as they likely won’t be supported by your recipient’s email client. Forms also aren’t supported in email across common email clients due to security risks. Instead, place a call-to-action button or a link to a landing page with a form in the body of your email.

6. ABC – Always be compliant

Last, but certainly not least, always comply with your local email laws. If you’re sending a newsletter, add unsubscribe links as required by your local laws. If ever in doubt, check out the CAN-SPAM Act of 2003 to refresh yourself on exactly how spam is classified. And remember, while US laws may seem strict, other countries have laws that are even tougher, so always check local spam requirements.

Spam blockers serve a great purpose – they keep our inboxes free from mail order brides and foreign princes who totally have $10,000,000 for us if we just give them our atm pin number. But the spam justice system isn’t always fair, and a lot of times, important content can get wrongly locked in email jail. Leave the spam with your flashlight and bottled water in your emergency earthquake kit, and follow these six tips to watch your email delivery and open rates skyrocket.


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