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What Causes Emails to Go to the Spam Folder?

What Causes Emails to Go to the Spam Folder?

Spam folder is a black hole for the emails and email marketers dread that a lot. Emails landing into the spam folders are the main reasons behind low email open rates of your email marketing campaigns.

Are the Emails going to the Spam Folder a Real Cause of Worry?

Spam emails are a major threat on the internet. That is why Internet Service Providers (ISPs) and Email Service Providers (ESPs) have become more aggressive in their spam-fighting efforts.

The majority of emails filtered as spam are, in fact, spam. As per Statista, more than 50% of the emails sent are spam. Such huge amounts of spam emails will surely irritate the recipients if they had to manually scan and filter them. Therefore, ISPs and ESPs set up filters to automatically remove spam emails before they land into the inbox.

Talking about the other side of the picture, roughly 1 in every 6 emails goes to the spam box or the recipient’s inbox blocks it. This is around 83%. Now you would wonder that 83% inbox delivery rate is acceptable. But, would you be content if you only made 83% of your earning potential?

You’re losing potential chances to earn revenue or acquire new leads that could have been made if your emails had arrived in your clients’ inboxes. Hence, you should pay close attention to why emails land up in spam folders.

Here are some main reasons and poor email marketing practises that may route your emails to the spam box.

Spam-like email Content Format

A strict NO is using spam trigger words that are too manipulative, demanding, deceptively promising, unethical, or evoking unpleasant feelings in the emails.

Emails with incorrect grammar and spelling errors always go to the spam folder (It’s because most of the spammers are non-native English speakers, who generally use translators to convert the text into English). Large fonts, typographical flaws, vivid colour schemes, and many signs and symbols in the emails, such as asterisks and exclamation marks, make them spam-worthy.

Suspicious Links and Shortened URLs in the Emails

Any link in the email that leads to a questionable site or a URL reported as malicious or fraudulent will end up in the spam folder. Another reason for this is when the email marketer uses email marketing software with a spammy backend to rewrite links for tracking the link clicks.

A popular tactic that spammers use is employing URL shortening services to mask a suspicious URL. Hence, resist using generic link shorteners in emails.

Email Design Format does not abide by the Protocols

Spam filters do not scan the images in the emails. Spammers often use this as a point of benefit by concealing the spam trigger words in the images and using neutral words in the email body. Henceforth, emails with a highly unbalanced ratio of image to text and image-heavy emails can start getting identified by the spam filters.

Some email recipients may not allow photos in the emails to load, making the emails look spammy and causing it to be classed as spam.

  • No subject line.
  • Missing ‘From’ name.
  • No opt-out link.
  • Absence of a valid mail address.

All of these above-mentioned factors contribute towards making an email ‘spammy’. Furthermore, if the email marketing software is not able to check and clamp down these missing elements in the emails before sending them, it pulls down your IP reputation and deliverability.

Spam filters slowly and steadily takes the feedback about most emails with similar ‘spam’ characters and will begin to direct them to the spam box.

Non-responsive Emails

Considering the fact that most of the emails are opened on a mobile device, an email and its content that does not render properly on it can prompt the recipient to mark it as spam. In line with this, Mailercloud provides access to email templates as well as email builder tools to design a responsive email template.

Flash, HTML forms, iframe tags, JavaScript make any email design non-responsive.

Embedded forms in the emails require the use of JavaScript in the submit buttons which can be a cause of concern. They make the emails look like spam. There are in fact many other scripts, CSS attributes and HTML tags that many email clients do not support.

Violation of Spam Laws

Buying email lists, misleading subject lines, not providing unsubscribe links, and inaccurate ‘Sender’, ‘From’, ‘To’, ‘Reply-to’ information are all violations of CAN-SPAM and GDPR rules that will ultimately convey the emails to the spam.

Broken HTML and different versions of HTML in the emails makes them clumsy and unreadable. This not just alerts the reader to mark the emails as spam, but it also is a red flag for the spam filters.

Unacceptable Email and Attachment Size

The email size is indirectly proportional to the email deliverability. Too large email size will forewarn the spam filters and affect the email deliverability rates. Thus, the email size plays an important role in making the emails genuine or spam.

Avoid adding any attachments in the emails for two reasons:

  • First, they trigger spam filters, as any attachment can be a potential carrier of virus or malicious files. This lowers the likelihood of the email reaching the intended recipient’s inbox.
  • Second, they can increase the email loading time, especially if the attachment is large.

 Poor Domain Reputation

Domain reputation is directly proportional to the email deliverability. Higher the domain reputation better will be the email deliverability rates, and vice-versa.

What results in a bad domain reputation?

  • A free email address is strictly prohibited inside a third party system (which is the email marketing software) as they have stringent DMARC regulations. Having a custom domain helps in this case. The custom domain and ‘from’ address will aid in better email delivery and will gradually establish a positive reputation.
  • An ‘OFF’ email volume and frequency with sudden fluctuations is always alarming in the email marketing world.
  • Spam complaints contribute to negatively affecting the domain reputation.

Some users may designate malformed or ambiguous email addresses as spam, adversely impacting the domain and IP reputation.

Poor IP Reputation

Improperly warmed-up IPs and IP servers that aren’t configured with suitable email headers, authentication parameters, and encryption may cause emails to end up in the spam folder.

If an ESP does not have a Transport Level Security (TLS) authentication for their IPs in situ, this will affect the IP reputation. No-reply email addresses in the emails also stir up the spam filters. This causes the IP reputation to suffer (as the emails will bounce).

(TLS is a means for encrypting email messages so that anybody other than the intended recipient cannot read the content.)

Improper Email Authentication

Email authentication simply implies that the domain owner grants authority to a third-party ESP to send emails on their domain’s behalf.

If the ESP fails to verify that the email authentication, like Sender Policy Framework, DKIM records, DMARC, is not set up correctly, then the emails go to the spam folder.

Age of the domain also matters a lot when it comes to analysing the factors responsible for landing the emails into the spam box. Spam filters are extremely careful in the early days of a new domain. Likewise, it is difficult to harm a sender’s reputation, if they have a track record of maintaining a decent email conduct, unless and until something terrible occurs while using the domain or IP.

Ineffective Email Engagement

Not having a list of genuinely interested list of contacts will result in poor email engagement rates, which leads to:

  • High bounce rates,
  • More spam complaints (paving the path for future emails to go into the spam box)

Absence of double opted-in, non-opted-in, and improperly segmented list will result in email marketing campaigns that will lack relevancy. Furthermore, they will not be in tandem with the target audiences’ interests. Mailercloud’s powerful email list segmentation feature helps to segregate the contacts on the basis of different parameters. So, the resulting campaigns are apt and ensure maximum engagement.

Furthermore, an out-of-date email list with inactive and obsolete email addresses will result in low engagement and high bounce rates. (The image below shows the example of an inactive email address bouncing back an email)

If you do this on a mass scale and regularly, spam filters will frequently penalise your domain or ISP. In turn, the chances of your emails being marked as spam considerably increases.


Understanding why emails go to the spam folder is a good place to start when trying to get them into the inbox. Knowing anti-spam laws and the logic behind spam filters will help in eliminating any spamminess in the email marketing campaigns.

Hemanti Pradhan

Hemanti Pradhan

I am Hemanti Pradhan, a Content Writer skilled in delivering technical as well as non-technical writeups. My portfolio covers a wide spectrum – from product documentation to lifestyle blogs & social media posts. When not writing, I indulge myself in drawing Zentagles & Mandala art.

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