Retrieve Activity Custom Fields using Salesforce Package.xml

Retrieve Activity Custom Fields using Salesforce Package.xml

if you try to retrieve Activities fields (Custom fields of Event/Task object) then use the below:

<types>
<members>Activity.CustomField__c</members>
<name>CustomField</name>
</types>

For More details:

http://theblogreaders.com/retrieve-activity-custom-fields-using-salesforce-package-xml/