Using a 2048bit DKIM key in Account Engagement

To request a custom 2048bit key for your Account Engagement account, please contact Salesforce Account Engagement support. 

NOTE: Using a custom 2048bit DKIM key will result in an warning within the Email Sending Domain table in Account Engagement's Domain Management page. The warning notes a "Custom DKIM Entry".
You can click on this to expand and see "Your account supports 2048-bit key custom DKIM entries. To optimize deliverability, work with your IT team or hosting provider to add this to your DNS entries." So long as your custom DKIM DNS entries remain in place, no further action is needed. Should any doubts arise, you can check DKIM authentication with a simple test. 

There are a number of third party tools that can assist with troubleshooting email delivery issues. While email testing tools (such as mail-tester.com, mailgenius.com, etc.) can assist with troubleshooting email deliverability, these tools are unaffiliated with Salesforce. Customers can choose to use such email testing tools or not at their sole discretion. We encourage customers to review any email testing platform’s privacy policy to fully understand how information will be treated and make an informed decision accordingly.