TocMail requires password authenticated IMAP access to your email account. You can setup your entire company, regardless of size, in less than five minutes. See the "Company Setup" article for instructions.
If you are an individual user, TocMail currently supports FastMail accounts using that @fastmail.com address. See the "FastMail" article for instructions on how to sign up for your free FastMail trial, and how to configure TocMail access.