Final answer:
AMPscript can be used to personalize a monthly newsletter by retrieving a subscriber's first name from a different data extension. This is achieved by using a lookup function within AMPscript to dynamically insert the subscriber's name into the message body during the send process.
Step-by-step explanation:
To display a subscriber's first name and the date of send in a monthly newsletter, when the subscriber's first name data is stored in a data extension not used in the send definition, we can utilize AMPscript. AMPscript is a scripting language for Salesforce Marketing Cloud that allows for the dynamic insertion of data into emails, SMS messages, and push notifications.
Using AMPscript, you can retrieve the subscriber's first name from the data extension with a lookup function. For example, Lookup('DataExtensionName', 'FirstName', 'SubscriberKey', _subscriberkey) would retrieve the first name where 'DataExtensionName' is the name of your data extension, 'FirstName' is the column containing the subscriber's first names, and '_subscriberkey' is the unique identifier for the subscriber. You then include this script in your email template to personalize each newsletter with the subscriber's first name upon send.