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Escaping the spam filter – 11 tips to improve email delivery rates!

As a successful email marketer, one of your biggest challenges is making sure the great content you’ve written reaches the inbox of your subscriber, and your email delivery rates are perfect. Even the most legitimate and conscientious marketers are able to achieve only a 79% email delivery rate because of the overtime being put in by spam filters and ISPs to reduce unnecessary inbox traffic and improving the user experience.

We know how much effort you put into your campaigns, and to make sure it reaches as much of your audience as possible, ContentNinja brings to you a simple list of do’s and don’t’s.

The beginner’s guide to improving email delivery rates – let’s go!


1. Comply with the CAN SPAM Act, 2003, violation of which can cost you $11,000 per offence (i.e. per mailing address that you send it to, which can be expensive). Some of the main points covered under this act are:

  1. Never use deceptive header information (name, reply-to email, subject)
  2. The mail must explicitly state that it is an advertisement, along with the company’s physical postal address.
  3. Provide an opt-out option (unsubscribe link) on the mail that remains valid for up to 30 days post the mail being sent.

2. Make sure your server isn’t blacklisted: You can use free tools like Free Email Blacklist Lookup, Spam Database Lookup to check if you’ve been blacklisted. Thankfully enought, these tools also help you see who has blacklisted you, so you can follow up with them and try to get yourself exonerated.

3. Analyze your Spam Score: Before sending out the email/campaign, check its spam scorel. Mailzak provides this service to its users so that they can check their mail’s spam rating before sending it out. Other free spam checking services websites are,, and

4. Include a unique subject title: Include words in your email header that are unique to your email, therefore making it less likely to be sent to spam. For example, using your company name in the header, the name of a familiar person, or names of other companies in your industry.

5. Have a healthy Image-to-Text ratio: Including beautiful images in your mail might create a strong visual impact on the user, but plays havoc with various email clients and devices. The images might not look as good on your phone, or might be forbidden by users who have switched on text-only emails.

Try not to include images at all. If you have to, make sure that the mail is not overloaded with creatives. The general rule of thumb is- for every image, have at least two lines of text. And if you can, make sure your images are optimized so that the email size stays as small as possible!

6. Avoid attachments: Nothing gets those spam filters beeping like big attachments, especially in .exe and .swf formats. AVOID attachments, period. Jpeg, png files are still okay, but if there’s something you want to share with your subscribers, use a Dropbox or Drive link and make your email more effective!

7. Include a text format of your HTML newsletter: This is a nifty way of keeping out of the spam folder, whilesimpultaneously making sure all your readers can see your email-  even the ones who have HTML-based content disabled.


  1. Don’t use words commonly used for spam: You’d think it would be obvious, but a lot of people still miss it. Don’t use words or symbols like “$$$”, “viagra”, “porn”, “fast delivery”, or numbers with too many zeroes! In your subject header and body, Avoid discussions of free money from a Persian prince or unbelievable rate of weight loss.
  2. Don’t use spam-ish return addresses: Don’t have a ‘from’ address with too many numbers, as it might get you filtered out – for example: or
  3. Don’t use bad code: Avoid HTML errors in your code – keep it as clean as possible! There’s a variety of online resources that let you check your code for errors, but there’s no replacement for a competent developer.
  4. Have long names for images: “Paris.jpg” is better than “12345_Paris_Albert.jpeg”. Unlike websites, image names do not get crawled over mail. However, in case the image doesn’t get loaded, the ‘alt’ tag in the code should still explain what the image is about.

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This list is not exhaustive, but we hope it helped you plan your emails a tad better. Any queries? Feel free to shoot us an email at

Author avatar
Mayank Gulati