Rules - Set language of message notification We need to set up a rule that will send an email in the language of the Customer of an order LANGUAGE.

But the Message notify action in rules takes the CURRENT user interface language... so that might be fr or en, depending on the path in fact. The recipient language might be different.

1-Can you tell me what selectors I should use to set the mail language to the customer language? I guess I need to change some kine of data-value?

2-And maybe you can point how I can easily find this in the future. Would DEVEL help? Something else?

thanks!
Consider investigating if the patch in comment #3 of issue # 1472316 might be of any help. Even though it is not the exact same question here, it may help to find inspiration about how to answer your question.

For more details about this issue, visit the question about  "Rule condition to check which language is used by the visitor?".