Malte,
About vpopmail admin interface i was refering Matthew Geddert (not Malte) post in this thread (http://www.openacs.org/forums/message-view?message_id=200533) not you. I´m sorry. It was my mistake 😟
Yes. Integrate webmail with Project-manager is part of our concerns and in fact the efforts to get webmail-system working over bincimap are related with scenario you describe. We already provide pop accounts using virtual users/virtual domains administered with vpopmail and now we can use this same folder structure and authentication over imap concurrently. Also bincimap plays nice with qmail. I am not sure about how this email infrastructure scales but Patrick Giagnocavo from Zill.net told me about Dovecot (www.dovecot.org) so i will take a look at it too.
I am playing now with project-manager/invoices/tasks/mail-tracking from CVS HEAD and i think i could evaluate efforts at Tekne to realize scenario you describe.
\Orzenil
