Multilingual support is essential. Now WooCommerce is included this becomes more apparent, as I cannot use (in a multilingual site) many functions at all. For example: In a multilingual website each product has as many versions as there are languages. Mailpoet shows all of these versions, but without differentiation. It is not possible to set up different emails for different languages.
The simplest solution would be, to add a language identifier to (for example) the product names in a popup list. That would allow to create different sets of emails easily.
The biggest problem I face in several websites is the lack of support for multilingual websites.