looking for new electronic fax solution (with API's)

Hello,
I am needing a new efax solution.  We've been using efax.com but it has been pretty unreliable. The specific items we need for this are as follows (and is why not every efax provider will work):

1. Incoming to designated fax inboxes at the Fax provider, retrievable via web browser (with potential multiple fax numbers going to individual inboxes, assuming these are also individual sub-accounts)
2. Incoming forwarded to email (as an option to #1)
3. Outgoing fax from ASP (classic) web page or VB application.  This entails a Windows API, usually either COM or .NET.
4. Outgoing fax from email attachments (where you can send an email to a fax service email address with your
document as an attachment, and the fax service will fax it out).
5. International send/receive capabilities
6. Scheduler server (optional)

Any suggestions, esp. one you've used that is pretty reliable.
Thanks,
Berne