The quick answer is: you can't.
To send an email to someone, that person must be in the Marketo database. If you have a csv file then you could upload those email addresses to a static list in Marketo, and then send to them. Ensuring you have valid consent of course 🙂
Note that your Marketo database can be a synced-in replica of a different database - for example, Salesforce. If you have the Salesforce / Marketo sync set up, then you are in effect sending to an "external" database. But I don't think that's what you mean.
Where is your external database stored?
Hey Samuel,
Just out of curiosity, Are you referring to sending an email from Marketo to leads that don't exist in your database but exist in the other/external database?
The quick answer is: you can't.
To send an email to someone, that person must be in the Marketo database. If you have a csv file then you could upload those email addresses to a static list in Marketo, and then send to them. Ensuring you have valid consent of course 🙂
Note that your Marketo database can be a synced-in replica of a different database - for example, Salesforce. If you have the Salesforce / Marketo sync set up, then you are in effect sending to an "external" database. But I don't think that's what you mean.