Configuring DKIM on Cisco Ironport (ESA)

Configuring DKIM on Cisco Ironport (ESA)

To configure DKIM signing for the Cisco Ironport, please follow the below given steps:

  1. Create a new signing key pair:
  • Go to Mail Policies >> Signing Keys
  • Click Add Key
  • Use DKIM_YYYYMM_DD as the format for the key name
  • Use a 2048-bit key length
  • Click submit

2. Configure global DKIM settings

  • Go to Mail Policies> Signing Profiles
  • Under DKIM Global Settings, click Edit Settings
  • Set DKIM Signing of System Generated Messages to Yes
  • Set use From Header for DKIM signing to Yes
  • Click submit

3. Create a separate signing profile for each mail domain/subdomain

  • Go to mail Policies> Singing Profiles
  • In the Domain Signing Profiles section, click Add Profile
  • Enter a name for the signing profile (e.g. example_com-DKIM)
  • Select DKIM as the Domain Key Type
  • Enter the domain name
  • Use s1 as the selector (or another arbitrary name if another service already uses s1)
  • Select relaxed for the header canonicalization (This allows for variations in whitespace)
  • Select relaxed for the body canonicalization (This allows for variations in whitespace)
  • Select the signing key
  • Configure the profile to sign the Standard This configures the gateway to only sign the following headers, so that DKIM will still pass when other mail systems add other, non-standard headers in transit (e.g. debugging headers):

“From; Sender; Reply Too Subject; Date; Message-ID; To, Cc; MIME-Version; Content-Type, Content-Transfer-Encoding; Content-ID, Content-Description”

  • Add The following additional headers to sign
  • BIMI-Selector
  • Specify Whole Body Implied for body signing
  • Uncheck all tags to include in the signature
  • Leave the users field blank
  • Click Submit

4. Enable signing for outgoing mail

  • Go to Mail Policies>> Mail Flow Policies
  • Click on the RELAYED (i.e. outgoing) mail flow policy (or create it if it does not exist)
  • In the Security Features section, set DomainKeys/DKIM Signing to On
  • Click Submit

5. Enable signing for bounce and delay messages

  • Go to Network> Bounce Profiles
  • Edit the bounce profile associated with the public listener where you will send signed outbound messages (e.g. Default)
  • Set Enable Use Domain Key Signing for Bounce and Delay Messages to Yes
  • Click Submit

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