The language direction of translation requests coming from a specific case is determined by the Case language and the agent (if owned by a user) queue (if owned by a queue) language. Inbound messages, comments, transcripts or description translations will use the Case language value as the expected source language, and the agent or queue language as the target. Inversely, outbound requests will use the opposite logic.
An email language pair direction cannot be changed and will draw from these values. To change the direction, you must change the values, and the selection will reflect the changes.
To change the case language, you need to change and save the Unbabel Language in the Case. For a standard and suggested Page Layout configuration, the field will be under the Details tab, and the Unbabel section:
Note: depending on the layout, the location of the field may vary, or the field may be absent all together - in which case changing the language is not possible.
Click the pencil icon to edit the field, and select a new language as shown below.
Finish by hitting the Save button. The changes are now applied.