You can do this by creating a default blank sub-topic for each map with a topic note containing the name of the map and then saving this as a map part which you use to insert subsequent sub-topics. You could also add default task info to this default sub-topic if you wish. The map name will appear in the body of Outlook tasks after sub-topics are synced with Outlook.
Alternatively you could MM's ability to sync a categories tag group with Outlook categories by creating a unique category for each map which you can then sync with Outlook. You can then create a default sub-topic with this category and save it as a map part which you can use as outlined above.
This approach has the advantage that categories are much easier to find and sort by than topic notes in both Outlook and MindManager. The only slight downside is that it complicates matters if you already use categories for other purposes in your maps and/or Outlook. Both programs can handle multiple categories within the category tag group, however, though if you are applying category colours MindManager has no capacity to display more than one colour for a topic.
For a guide on how to sync tasks and categories between MM and Outlook, see my series of posts on doing this (and setting up dashboard maps as well) which starts here: https://sociamind.wordpress.com/2015/01/19/using-mindmanager-dashboard-maps-with-outlook-part-1/