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SPF (Sender Policy Framework) is a security standard for email sender verification. Its main purpose is to prevent the misuse of your email domain for sending spam or phishing emails. The basic principle of SPF involves publishing a special record in DNS (Domain Name System) that defines which servers can send emails on behalf of your domain.

How SPF Works

An SPF record is a type of TXT record in DNS and contains a list of IP addresses or domains that are authorized to send emails for a given domain. The receiving email server can look up this record and verify whether the email was actually sent from an authorized server.

Creating an SPF Record

1. Identifying Sending Servers: First, determine all the servers or services that send emails on behalf of your domain. This may include your internal email servers, Cloud services like Gmail or Office 365, marketing platforms, etc.

2. SPF Record Format: The basic format of an SPF record is "v=spf1 <rules> -all". <rules> can include IP addresses (using ip4: or ip6:), domains (include:), or special commands (a, mx, ptr).

3. Publishing the Record in DNS: After assembling the record, it needs to be entered into the DNS as a TXT record for your domain. The name of the record should be empty or @, which indicates the root domain.

Examples of SPF Rules

• v=spf1 ip4:192.168.0.1 -all: Allows emails only from the IP address 192.168.0.1 and prohibits all others.
• v=spf1 include:_spf.google.com -all: Allows emails sent from servers defined in _spf.google.com and prohibits all others.
• v=spf1 a mx -all: Allows emails sent from IP addresses associated with the domain's A record and MX records.

Common SPF Issues and Solutions

• Evaluation Limit Exceeded: SPF records have a limit on the number of DNS lookups. If your SPF record requires more than 10 lookups, verification may fail. The solution is to optimize the record, for example by merging include rules.

• Domain Spoofing: SPF does not address cases where the displayed sender name is forged. To provide further protection, combine SPF with DKIM and DMARC.

• Record Updates: If there are changes to email servers or services, it is necessary to update the SPF record to reflect the new configuration.

Proper SPF setup is key to protecting your email communication and improving the deliverability of your emails. Always plan and test changes to SPF records thoroughly to ensure correct verification processes and minimize the risk of message non-delivery.