Spam filters proactively monitor incoming emails to detect unsolicited emails and route them to the spam/junk folder. Like other automated programs, it works a certain way to identify the possibility of incoming emails as spam.
Before we delve into the discussion of how spam filters work and how to avoid them getting triggered, let’s first analyze what spam is.
What Is Spam?
A large percentage of email messages sent globally are categorized as spam. In some countries, the commercial email industry is governed by legislation and regulation.
Some of these countries are the USA (CAN-SPAM ACT), Canada (CASL), Australia (Spam Act 2003), the United Kingdom (EC Directive 2003), and Germany (Federal Data Protection Act).
All the laws and regulations may have their peculiarities, but collectively all of the anti-spam laws emphasize the use of opt-in forms to collect contact information, send permission-based emails only, and provide an easy way to opt out as well.
So more precisely, spam is an unsolicited and irrelevant electronic message sent in bulk to a large number of contacts, and without their prior permission.
So the crux of spam filters is that they are striving to limit the possibility of such unsolicited and irrelevant emails entering the recipient’s inbox. Spam filters are getting more efficient with time and utilizing a variety of ways to identify and categorize email spam accurately, but they aren’t perfect and it is often observed that even some of the major ISPs route a completely legitimate message to spam/junk folder.
Therefore, knowing about spam filters is important for achieving the target of high inboxing. Spam filters don’t offer the details of practices to follow and things to avoid, but still, it is obvious that they are programmed to implement anti-spam laws effectively.
Here are a few of the factors spam filters would take into account to determine if the incoming message is spam.
Message Header/ Originating Source
Spammers mostly conceal the message-originating information to avoid getting traced. Therefore, spam filters put effective tools to scrutinize the email header and relay information left by the sending server.
It considers several useful factors to look into from and reply to (return-path) information, subject line, and unsubscribe header. It looks for the validity of the DKIM signature and also if the originating server is allowed to send on behalf of the sender (SPF).
A spam filter triggers if it finds that the email header is forged and the incoming email is potentially spam. So always avoid using deceptive information in your header.
Moreover, if you are using an IP address that has already been identified for relaying spam, trapped, and listed publically by one or more recognized blacklist(s), your email is more likely to be ended up being filtered as spam. Always rely on the IPs having a clean sending reputation and history.
Content filters are working from the very beginning to distinguish legit emails from emails with spammy stuff. Sender behavior has educated the spam filters to detect the typical kind of email content used to steal the recipient’s identity or important information by making him click on a fraudulent link. Or the type of words/ phrases used in large-scale advertisement campaigns about easy money-making, earing, trading and more.
More clued-up spam filters vigilantly detect words and phrases used by the spammers and place the email with such words/phrases in the spam/junk folder. Unluckily, we don’t have a complete list of words/phrases filters considered spam, but a still large number of such words/terms are available on the internet to avoid them getting used in the email content.
The content filters can be discussed for the extra ability to be triggered for a certain types of images and messy codes. Therefore, do properly format the email content; avoid using forms, all letters in caps, fonts of too large sizes, and doing other strange things with the email content like bilking words/texts. Make use of a subject line that denotes the content of your email campaign. Avoid all kinds of tricky and deceptive practices.
There are certain other clues that the sender would give to the spam filter to identify the email as spam. But since, the working of every spam filter is different from the others and spam filters don’t publish any such detailed criteria to meet for avoiding getting spammed. We can only follow the largely accepted industry standards, spam laws, and best practices.
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