No announcement yet.

How to Keep your Email out of the Spam Folder

  • Filter
  • Time
  • Show
Clear All
new posts

  • How to Keep your Email out of the Spam Folder


    This article contains helpful information to make sure that other servers or network do not mark your email as spam.

    Prevent email abuse on your server

    You do not want to send spam from your server. For more information on how to make sure that you do not send spam, read our How to Prevent Email Abuse documentation.

    Use Email Authentication (DKIM and SPF)

    DKIM (Domain Keys Identified Email) and SPF (Sender Policy Framework) authentication can help verify that email comes from a trusted sender. DKIM is a validation system designed to detect email spoofing. It provides a means for your mail server to check email that comes from a domain is authorized by that domain's administrators. The email includes a digital signature that your mail server uses to verify the senders public key in their DNS record.

    SPF uses DNS records to prevent email spoofing. If an email message uses fake sender addresses, SPF uses the DNS record for the sender's domain to detect the modification in the email's header.

    Note: On servers that run CentOS 7, you may see a named warning about the absense of SPF resource records on DNS.

    A. This warning is not relevant on CentOS 7 servers, because RFC 7208 deprecated SPF records. CentOS 7 servers use TXT records instead of SPF records.
    B. Red Hat may update the bind RPM to comply with RFC 7208 in the future. For more information, read the Red Hat Bugzilla case about SPF record errors.


    DMARC (Domain-based Message Authentication, Reporting & Conformance) is a technical specification to help reduce the potential for email-based abuse. A DMARC policy uses DNS to confirm an email message has a valid DKIM and SPF record, but also that the From: header matches those records. Many large email networks require that you use a DMARC policy to help protect their users from spam email. To prevent email rejections or spam flags within these networks, your server must use a DMARC policy.

    Configure your server's PTR record

    In DNS, a PTR record resolves an IP address to a domain name. A PTR record is similar to an A record, but in reverse. You should configure the PTR record of the primary IP address of your server to use the hostname of your server. If you have configured EXIM to use a different IP address, the PTR record of that IP address should use the hostname of your server.

    Example of an A Record:
    server:~ root$ dig +short
    server:~ root$

    Example of a PTR record:
    server:~ root$ dig -x +short
    server:~ root$

    Other networks mark my email as spam
    If email networks, such as Google, Yahoo, or Outlook, mark your server's email as SPAM, you must identify the reason and resolve the problem. If you have recently resolved an issue with spam on your server or you received a new IP address which previous sent spam, you will need to notify the remote network. You should take the time to review the bulk sender policy of large email networks.

    Bulk email best practices
    1.Use the same IP address to send all bulk email.
    2.Use the same email address in the From header of your email.
    3.Ensure your email complies with RFC5332.
    4.If your email uses HTML, ensure it complies with HTML standards.
    5.Ensure the contents of your email body is relevant to the subject of your email.