Spam filters use a lot of different criteria to judge incoming email. Each factor is weighed and added up 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 permission-based lists can get flagged by aggressive spam filters. The best way to avoid these false positives is to better understand how spam filters work. In this article, you'll learn more about spam filters and how to determine if you have a problem with your content.

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. Here are some of the common things spam filters look for and how to avoid them.

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. Spam filters will also look to see if you're already on your recipient's contact list. Spam filters usually judge senders that use anonymous and free email addresses for their "from" email, such as Gmail, more harshly than verified domains. However, even private domains will develop their own good or bad sending reputations, so it can be risky to send a big campaign from a brand new domain before your reputation is established.

Your IP Address

Some spam filters will flag your campaigns if anyone with the same IP address has sent spam. When you send campaigns through Upsales, your content is delivered over our servers. That means if one person decides to send spam through Upsales, it could affect deliverability for our other users.

Content and Format

Campaign content should be clear, clean, and balanced. Private domains and some Internet Service Providers (ISPs) may have more aggressive spam filters that flag emails based on specific content or images. There aren’t any hard and fast rules to format.

• All of your subscribers should have opted-in to your list and be familiar with your brand
• Design your campaign content with your specific audience in mind, but keep visual branding consistent. Ideally, the design of your Upsales campaigns should match content found on your social profiles and website
• Be sure all your links are valid and avoid link shorteners

Code

'Sloppy code, extra tags, and code pulled in from Microsoft Word can trigger spam filters. We recommend you use one of our templates or work with a designer.

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 and test your campaigns.