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Spam Filters

Before you send out an email campaign, make sure you’ve created a newsletter sure to go sail through spam filters and land in your recipients’ inbox folder. If your message lands in the spam folder, most likely it won’t be read. Who really reads through their spam folder?

I’ve summed up some of the most important information on how to correctly prepare a newsletter. Also, what to include and what avoid in order for your email to land in the inbox folder rather than the spam folder and increase your email open rate and return on investment (ROI).

Spam filters are installed on email servers of companies as well as Internet and email service providers in order to be protected against unsolicited bulk messages.
Spam filters on email servers are installed at different levels. For example, a hard spam filter means your message will land in the spam/junk folder if it contains large images, large attachments, incorrect links, spam words in content or subject line, forms and scripts, long subject lines or if you have a bad sender reputation. Meanwhile, low spam filtering means your message will land in the spam folder only if it contains a lot of spam words.

WHY YOUR EMAIL MAY LAND IN THE SPAM FOLDER

Large images in your email content

Don’t include images over size 1 MB and 600 pixel width. Images shouldn’t take up more than 50% of the whole email. It’s better if the majority is text. Read more about HTML email guidelines.

Incorrect links

If the email contains non-existent or incorrect links, it may land in the spam folder. If you tract HTML clicks within HTML campaigns, we do not recommend inserting links that begins with http:// because Internet service providers (ISPs) can identify them as SCAM and forward to the spam folder. In HTML messages, email software often automatically recognizes text as links starting with http:// . And if this text already contains a link, it may seem very suspicious and these messages are often caught by spam filters.

Spam words in the email content and subject line

Email Servers’ anti-spam software are made to catch emails containing specific words or word combinations in the email content or subject line. It is also possible to manually enrich this spam list by typing spam words and criteria, and then watching what will happen if spam filters recognize potential threats in the email. Most email service providers use third-party services like Cloudmark to keep their spam word list database up-to date.

Here you can see the list of TOP 1000 spam-words.
Read more on which words avoid in emails.

Large attachments

If you want your email campaign to be delivered as fast as possible, do not attach large files. Our recommended size of attachment is up to 1MB, maximum – 10 MB. Make sure you have reduced the attachment size as much as you could.

Forms and scripts in email content

Do not insert scripts and forms in email content. Almost all email programs block script codes. It means that even if the recipient receives your message, forms and scripts will not work anyway.

Long subject lines

Do not write subject lines longer than 50 characters. Most email programs do not have the space to display subject lines consisting of more than 50 characters. Also, leave the most important information for email content. Once again – beware of spam words in the email subject line.

Emails are not opened for a long time

Some ISPs practice the following: if your sent emails are not opened for a long time, then your further emails for the same recipient will land in spam folder. To land them in inbox folder, the recipient must open at least some of your messages or you have to change the sender IP.

One of the most popular spam filters is SpamAssassin. Mailigen has set up this filter in order for you to check the spam score of your email campaign in the STEP4. If your score is high, it will affect campaign delivery to the inbox.

If you want to find out more about delivery or want to improve your results, please contact our team and we will help you.

View list of spam words you should avoid in subject lines.

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