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Spam filters and how they work

Last updated by Adrin Siripala on November 08, 2016 13:24

Spam filters use a lot of different criteria to assess incoming emails, (including your marketing emails). Each criteria is assessed and added to assign a spam score, which determines if a campaign will pass through the filter. Passing scores vary depending on the server, so a campaign might pass through some filters but not others.

Even compliant senders with opted in permission-based lists can get flagged by aggressive spam filters. The best way to avoid these false filters is to understand better how spam filters work. Below, you'll learn more about spam filters and how to minimise your risk and maximise your sending and receiving rates:

What Spam Filters Look For

Because different spam filters can function slightly differently, it can be difficult to nail down the exact criteria for judging spam. However, there are some basic characteristics of spam that tend to hold true. Below are some of the common things spam filters look for and how to avoid them.

Subject Lines:

Subject lines are a critical component of effective email marketing. Subject lines that are irrelevant or contain a lot of capital letters and excessive punctuation (inc the £ sign and % sign) tend to trigger spam filters. Avoid words like "FREE," "buy now," "crazy offer just for today".

To view our great support guide on writing effective subject lines click here

Email Campaign Content and Format:

Your campaign content should be clear, clean, and balanced. All of your subscribers should have opted-in to your list and know who you are. Any kind of blurb or introduction to your company could look like an advertisement and could trigger spam filters.

Avoid financially-motivated content, such as offering a chance to win money or reduce debt, and keep a balance of images and text in your content. Be sure all your links are valid and avoid the full url being the linked text, to avoid Phishing messages.Best to use clickable text at the front, with the full url behind.

Click here to see our InTouch support guide on words to avoid in your campaigns.

Generally avoid all CAPITALS and extra exclamation points anywhere in your content. Spam filters will also check to see if a plain-text version of the campaign is available. With all our InTouch system templates (and bespoke builds) the plain text alternative is auto-built in, as is the unsubscribe link.

Campaign Metadata:

Spam filters want to know that you are acquainted with the person receiving the email. Spam filters are more likely to flag your email if your email is addressed to your recipient's email address and not their name. We recommend you personalise your email e.g. Hi %FirstName% and use the editor tags and links.

Spam filters usually judge senders that use anonymous and free email addresses for their "from" email, such as Gmail, more harshly than verified domains.(check your Email approval list)

Ask your contacts to add your from Email address(es) to their address book or safe senders list, to strengthen your send/receive rate.

Your IP Address:

We work vigilantly at our end to keep our sending reputation intact, so it's important that you do your part to abide by our Terms of Use. Your reputation affects our reputation, as your emails are sent through our InTouch servers, so we want our business relationship with you to be a win, win! We are happy to coach you and have a review of your email campaign stats in the process so just ask us for training!

Our support site is packed full of advice. Just click here and search for what you need.

Html Code:

Sloppy code and code pulled in from Microsoft Word can trigger spam filters. For front-end content with Word it is always best to paste into Notepad first, then into your campaign. Notepad will strip out most of the back-end code from Word to avoid the potential clash with our InTouch back-end code.

We recommend you use one of our templates or ask us to quote you for a custom build or tweak of one of our system templates.

The Big Picture

Spam is a real issue and should be taken seriously by everyone in the email community. For the most part, avoiding spam filters is about staying compliant and understanding how your campaign looks in its entirety. Spam filters use sophisticated algorithms to analyze a lot of email with a long list of criteria to consider.
The big takeaway is that if something about your email triggers a spam filter, it will likely take a closer look but generally, your campaign would need to have multiple triggers to get filtered as spam. Always stay in compliance, test your campaigns, and take advantage our Support guides. Click here for another useful guide