Emails can be flagged as spam due to a combination of content-related, technical, and behavioral factors. One common reason is the use of spammy or overly promotional language, such as excessive use of spam words like “free,” “buy now,” or “guarantee.” These keywords, when paired with elements like excessive punctuation (e.g., “!!!”) or capitalization (e.g., “LIMITED TIME OFFER”), can trigger spam filters. Poor email formatting, such as using too many images relative to text or including suspicious links, also raises red flags.
On the technical side, misconfigurations in email authentication protocols like SPF, DKIM, and DMARC can result in emails being flagged as spam. Without these properly set up, email providers cannot verify that your messages are legitimate, which makes them more likely to be blocked or sent to the spam folder. Another major cause is sending emails to outdated, invalid, or purchased email addresses without bulk verification. This increases the chances of high bounce rates and spam complaints, signaling to email providers that your domain is untrustworthy.
Additionally, low engagement rates, such as recipients not opening your emails or marking them as spam, negatively affect your sender reputation. A poor reputation can cause even legitimate emails to be flagged. Email providers use sophisticated algorithms that consider all these factors, so a holistic approach to content, technical setup, and audience engagement is essential to avoid being flagged as spam.