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Much is said about avoiding the spam folder and ways to improve deliverability. ?Every marketer wants to be read, or else any effort in delivering engaging content is in vain.

Even though spam traffic worldwide has been decreasing for the past years, more than half of all email today is still spam.⚠️

If you want to address spam properly without an unnecessarily loss of revenue, you should know exactly what takes your email to spam.

Spam filters are part of the email game, and guess what? They are there to help both you and your customer. Spam filters help your most relevant emails avoid getting lost in the middle of a ton of crap while keeping your customer’s inbox clean from scams and unsolicited messages.?

They function through algorithms based on Bayesian probability, i.e., they come up with a score which represents the level of reasonable expectation that a certain email is spam.

So, what do they look at?

?   Who is sending it?

Spammers have been using abusive practices for a long time. For instance, they constantly change IP addresses and domains in order to escape a bad reputation.

For this reason, spam filters consider the age of IP addresses and domains.

Newer IP addresses are seen as risky by inboxes. No wonder you’ll need to warm your IP first if you opt for a dedicated IP address.

In addition, your sender reputation is monitored and quantified by things like the number of spam complaints, volume and blacklists, so all of these are important for your overall sender score.?

P.S: Unless you use a dedicated IP address, your sending IP is provided by your ESP,Klaviyo or Mailchimp for example, and your reputation should be built within the parameters established by the ESP. The same applies for sending domains.


?Email content

This is a simple one, yet overlooked by many marketers. Nowadays, with advanced content analysis technology, inboxes evaluate the email source code and its overall content structure.

This means that, after your email has made it through the first filtering process based on sender reputation, the full content of your email is analyzed. ?


Anti-spam algorithms are constantly learning from user feedback through indicators such as:

▶️Mark email as non-spam

▶️Messages read

▶️Spam complaints

▶️Messages replied to

▶️Sender added to the recipient’s contact list

▶️Forwarded messages


Unfortunately, it is not possible for us to track most of these metrics. However, we can make use of proxy metrics such as open and click rates. This is a whole new topic, but if you’re not doing spam diagnostics, you should definitely reach out and get help.

?Still, the bottom line is that each inbox provider has its own particularities in how they evaluate message content. The exact algorithms are very advanced and ultimately held secret.


Nevertheless, there are a few things you should always consider:

▶️Reduce image sizes.

▶️Reduce the source code.

▶️Avoid too many links.

▶️Balance text and images ratio.


??Needless to say, it all comes to testing. Test, test, and test. Learning best practices and applying them is only the starting point of your journey to the inbox. All this might feel overwhelming, so start small and don’t try to get everything right from the get go. But also don’t ignore this. Sending emails without at least the basics of deliverability will definitely result in flagging your domain and landing into spam.

The G-lock spam testing tool can be of great help in figuring out how you can adjust content for better deliverability. ? From there, you can use the feedback data of your tests and optimize your email content.


Rodrigo, Hustler Marketing

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