Not Moose and Squirrel.
Although it seems that way.
Customer wants to standardize on the Lotus platform but has people using Outlook, Thunderbird, Evolution and Squirrel.
Migrating from Outlook or Outlook Express to Lotus Notes is fairly easy using the built-in tool when you install your Notes client. Mail, Folders, Calendar and contacts.
Squirrel which is a front end GUI to a back end Linux server you can use IMAPcopy. they even show a chart of all the IMAP solutions they work with, Domino 8.5 is on the list.
Evolution I think may fall under the Squirrel option.
Thunderbird I am still looking for more details but may follow Squirrel too.
Any thoughts or other options please leave me comments or email/IM me from the links above.