I noticed that when I copy/move emails from a non-alfresco email account into an Imap mounted alfesco account (Drag & Drop in Thunderbird) Umlaute get unrecoverably garbled. When I reverse the process, ie. dragging the damaged email back into the non-alfresco email folder it stays messed up. I thus presume that alfresco does not store emails as it would for instance any other sort of binary documents, ie. 1:1 copies.
sorry about not making clear the question "Is this correct?". What I meant was whether or not my assumption was correct, ie. that alfresco does not import a 1:1 copy of the email into its repository but rather a "transformed", or in the case of the email containing umlaute "malformed" version of the original email.