Error deploying process to scratch org: "A condition has a reference to... which doesn't exist."

Question

We have a process which has this criteria:

The XML metadata for this workflow has:

            </conditions>
                ...
                <leftValueReference>myVariable_current.RelatedToId</leftValueReference>
                <operator>StartsWith</operator>
                <rightValue>
                    <elementReference>formula_2_myRule_1_5825545192</elementReference>
                </rightValue>
            </conditions>

The error appears to be complaining about the left side operand, myVariable_current.RelatedToId, which in the flow (shown in the image above, in the popover) is [EmailMessage].RelatedToId.

Are we missing some scratch org config setting to enable email in scratch orgs? This process is already deployed to other environments with the same metadata, so it's unclear what's causing this.

Answer 1

As hinted at by the comment, this feature comes from the "enhanced email" setting. I fixed the error by enabling that setting in a scratch org:

"settings": {
    "emailAdministrationSettings": {
        "enableEnhancedEmailEnabled": true
    }
}