Policies - Anti-Spoofing SPF Bypass

This article contains information on configuring an Anti-Spoofing SPF-Based Bypass policy, including considerations for domain entries, policy settings, and limitations related to SPF record validation.

Anti-Spoofing SPF-Based bypass policies allow 'spoofed' inbound messages through to end users that you consider to be legitimate. This could include emails generated from web servers that hold your domain name or a trusted third-party system that generates emails using an internal email address.

Usage Consideration

Consider the following before creating a policy:

• • • Only one Anti-Spoofing SPF-Based Bypass policy can apply to a specific mail flow, but it can contain many domains.
    • Don't enter domains with a "+all" qualifier in their SPF record, and always validate a domain's SPF records prior to entering it in the policy.
    • If you want to allow your company domain/email address to be included in the Anti-Spoofing Bypass policy, you must specify the internal address/domain that you will allow to be spoofed. In this case, you should not also be listing the external sending address that may also be appearing in the sending header/envelope.

      There are limitations in the algorithm used to validate SPF records. If an SPF record has 10+ terms (include, redirect, etc.), an Anti-Spoofing SPF-Based Bypass policy does not apply. If a sender is using an IP address contained in an entry processed after the 10th term, the SPF check fails. This can occur for organizations that use multiple 3rd party services to send mail containing their company domain name.

Configuring an Anti-Spoofing SPF-Based Bypass Policy

To configure an Anti-Spoofing SPF-Based Bypass policy:

1. Log in to the Mimecast Administration Console.
2. Select the Policies | Gateway Policies menu item. The Gateway Policy Editor is displayed
3. Click on Anti-Spoofing SPF-Based Bypass.
4. Either select the:

• • • Policy to be changed.
    • New Policy button to create a policy.

5. Complete the Options section as required:

Field / Option	Description
Policy Narrative	Provide a description for the policy to allow you to easily identify it in the future.
Select Option	Select whether to enable or disable the bypass policy. If enabled, none of the Anti-Spoofing policies will be applied if the inbound IP address is referenced on any of the SPF records of the domains specified in the “When IP matches SPF records of” field.
When IP Matches SPF Record of	Specify the domain names whose SPF records should be checked to see if the connecting IP address has been referenced. This acts as a policy condition if an SPF check for the connection IP address results in a “Pass” or “Success” for any of the entered domains. The bypass is then applied if the communication pair matches the policy "from" and "to" configuration.
Applies From	Set to a value of from "Everyone" to "Everyone" as long as the value entered in the "When IP Matches SPF Record of" field matches the domain.
Applies To

6. Complete the Emails From and Emails To sections as required:

Field / Option	Description
Addresses Based On	Specify the email address characteristics the policy is based on. This option is only available in the "Emails From" section: Both: Applies the policy based on either the Mail Envelope From or the Message Header From, whichever matches. If both match the specified value, the Message Header From is used.
Applies From / To	Specify the Sender characteristics the policy is based on. For multiple policies, you should apply them from the most to the least specific. The options are: Everyone: Includes all email users (i.e., internal and external). This option is only available in the "Emails From" section. Internal Address: Includes only internal organization addresses. External Address: Includes only external organization addresses. This option is only available in the "Emails From" section. Email Domain: Enables you to specify a domain name to which this policy is applied. The domain name is entered in the Specifically field. Address Groups: Enables you to specify a directory or local group. If this option is selected, click on the Lookup button to select a group from the Profile Group field. Once a group has been selected, you can click on the Show Location field to display the group's path. Address Attributes: Enables you to specify a predefined attribute. The attribute is selected from the Where Attribute drop-down list. Once the Attribute is specified, an attribute value must be entered in the Is Equal To field. This can only be used if attributes have been configured for user accounts. Individual Email Address: Enables you to specify an SMTP address. The email address is entered in the Specifically field.

7. Complete the Validity section as required:

Field / Option	Description
Enable / Disable	Use this to enable (default) or disable a policy. If a date range has been specified, the policy will automatically be disabled when the end of the configured date range is reached.
Set Policy as Perpetual	If the policy's date range has no end date, this field displays "Always On", meaning that the policy never expires.
Date Range	Use this field to specify a start and/or end date for the policy. If the Eternal option is selected, no date is required.
Policy Override	This overrides the default order that policies are applied. If there are multiple applicable policies, this policy is applied first unless more specific policies of the same type are configured with an override.
Bi-Directional	If selected, the policy is applied when the policy's recipient is the sender, and the sender is the recipient.
Source IP Ranges (n.n.n.n/x)	Enter any required Source IP Ranges for the policy. These only apply if the source IP address used to transmit the message data falls inside or matches the range(s) configured. IP ranges should be entered in CIDR notation.

8. Click on the Save and Exit button.

See Also...

• • • Configuring Anti-Spoofing
    • Gateway Policy Editor