Markus Grandpré writes:
When migrating the lists and archives from Mailman 2.1 to Mailman 3, the e-mail templates were obviously not migrated.
Which templates? Headers and footers are in the database, and they should be migrated. The standard templates for autoreplies, moderator notifications, and so on will have versions appropriate for Mailman 3, and as far as I know all of the languages standard in Mailman 2 have been translated to Mailman 3, or the Mailman 2 version crudely adapted to Mailman 3.
Do you mean custom templates (such as moderator noifications) that overwrote stock templates in the Mailman 2 installation? I would think you would have to copy those by hand, because the upgrade process would not know that they're customized, and would just assume the new installed versions are good for you. I'm pretty sure you can copy them to a different place that has higher precedence in the search path so you don't have to worry about them being overwritten by upgrades.
Unfortunately Mark is on vacation.
Steve