Mailing lists, such as the UT List service, generally modify messages via subject tags, body footers, attachment stripping, and other useful features that break the DKIM signature, which in turn fail external email provider's DMARC policies. 

When a mailing list chooses to implement Sympa's DMARC workaround, the following steps happens to the email before being distributed:

• The DKIM and DomainKey signatures will be removed.
• The From field will be changed to a value that the list owner chooses. If left blank, the list email address will be sent instead of the original sender address.
• Previous value of the From header is saved in an X-Original-From header for later inspection.
• Previous value of the DKIM signature is saved in X-Original-DKIM-Signature for later inspection.

Note: The UT Lists team recommends setting the protection mode to DMARC policy suggests rejection. Only list owners may enable/disable DMARC workaround.

To use the DMARC workaround, follow these steps:

1. Log on to UT Lists and select your list from the My Lists option.

   

2. Select Admin from the left hand menu.
3. Hover over Edit List Config and select the DKIM option.
4. From here, select what messages you'd like the DMARC workaround to be used from the list of Protection modes.
5. For the purpose of this workaround the UT Lists team recommends setting the protection mode to "DMARC policy suggests rejection(dmarc_reject)"