It's a pure email client! We do not have a third party server processing your emails, your data goes only directly between your computer and your email server.
Found it on your website:
> Total privacy - we do not have access to your email account, Ivelope only sends your email data and password between your computer and your email server.
A question, is it a pure email client, or an email client behind a value added service (it relies on a server you run somewhere)? Thanks!