I want a web-based e-mail service which
displays e-mails sorted by conversation;
can import e-mails from POP3 accounts;
can send e-mails from other accounts (either by faking the
Fromheader or by logging into that account's SMTP server);
is hosted in a location which is subject to the EU Data Protection Act;
is not subject to the US PATRIOT Act (hence, not run by an EU subsidiary of a US company);
provides a large amount of storage space.
I do have a shared hosting account in the UK, so if there's any FOSS software I could install there, that'd be good, but I'm mainly looking for a service provider to handle it for me.