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Eloqua Analytics Documentation
Note that in this video it says you can't upload custom data objects, this has since been fixed. It is recommended that if you intend to use a variable in your email ("Dear First Name"), you upload your contacts using custom data objects. The file below gives you the template you need, and you can follow the Eloqua documentation for Uploading records to a CDO. Uploading contacts this way is often slower than using the regular contact uploader, so do so well in advance of when you need it.