Emails can be blocked for several reasons, primarily related to security, spam prevention, and compliance with email service policies. Here are the main reasons and examples:
Spam Detection: Email providers use algorithms to detect spam. If an email contains suspicious content, links, or attachments, it may be blocked.
Example: An email with multiple links to unknown websites or generic greetings like "Dear Customer" is often flagged as spam.
Phishing or Malicious Content: Emails attempting to steal personal information or containing malware are blocked.
Example: An email pretending to be from a bank asking for login credentials is flagged as phishing.
Blacklisted Senders: If the sender's IP address or domain is listed on a spam blacklist, their emails are blocked.
Example: A company using a shared server that was previously abused for spam may find all its emails blocked.
Email Content Violations: Emails violating the recipient's email provider policies (e.g., excessive promotional content) may be blocked.
Example: Sending bulk emails without proper opt-in consent can lead to blocking.
Incorrect Email Configuration: Misconfigured email servers (e.g., missing SPF, DKIM, or DMARC records) can cause emails to be marked as spam or blocked.
Example: An email server without SPF records is more likely to be flagged as untrusted.
Recipient's Filters: Recipients may set up custom filters to block specific senders or keywords.
Example: A user blocks all emails containing the word "discount" in the subject line.
To ensure emails are delivered successfully, especially for businesses, using reliable email services and following best practices is crucial. For example, Tencent Cloud's email delivery service provides tools like SPF, DKIM, and DMARC configuration to improve email deliverability and reduce the risk of blocking. Additionally, its anti-spam and security features help maintain a good sender reputation.