As mentioned above, they must be automated marketing emails and as per the article there are a few limitations:
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If you insert a custom object personalization token into your automated marketing email, it will only render the associated property if you're using the email in a workflow based on your custom object.
If the name of your custom object contains a hyphen (e.g., custom-object), the email will not be able to render personalization tokens for properties of that object. Learn how to edit the name of your custom object.
If you select a date property (e.g., Date of last meeting booked in meetings tool), the date will be rendered in your email, but the time and timezone data will be omitted.
As mentioned above, they must be automated marketing emails and as per the article there are a few limitations:
"
If you insert a custom object personalization token into your automated marketing email, it will only render the associated property if you're using the email in a workflow based on your custom object.
If the name of your custom object contains a hyphen (e.g., custom-object), the email will not be able to render personalization tokens for properties of that object. Learn how to edit the name of your custom object.
If you select a date property (e.g., Date of last meeting booked in meetings tool), the date will be rendered in your email, but the time and timezone data will be omitted.