Mailchimp

Use the Workflow for "EditMember", see an option for Mailchimp. First setup the Mailchimp API on Admin Settings > Mailchimp API.

In the workflow, set this to run for ALL roles or just specific roles.

Whenever a user is edited, the user will be pushed to Mailchimp. If the user has unsubscribed from Mailchimp no change is made.

If a user unsubscribed to all emails within the Mition portal an unsubscribe is set to Mailchimp.

Campaign Monitor

Use the Workflow for "EditMember", see an option for Campaign Monitor. First setup the Mailchimp API on Admin Settings > Campaign Monitor API.

In the workflow, select a List ID (to send users to a specific Email List), select which tags to match on Users and set this to run for ALL roles or just specific roles.

Whenever a user is edited, the user will be pushed to this Campaign Monitor list. If the user has unsubscribed from Campaign Monitor no change is made. If a user unsubscribed to all emails within the Mition portal an unsubscribe is set to Campaign Monitor. 

XERO

See more information on Xero Setup here