ftpx.org
Managed file transfer is a real enterprise category with compliance requirements and serious budgets, dominated by proprietary tools. An open alternative would find an audience, and the .org is where such a project would live.
FTP is one of the oldest protocols still in daily use, and file transfer as a problem has outlived it several times over. FTPX reads as the next thing after it, with the X suffix signalling extension or successor without claiming to be a specific standard. Anyone technical reads it immediately.
The name suits a transfer product, a managed service, an open protocol project, a standards initiative, or a technical resource.
Four characters, no hyphen, entirely legible to the technical audience, short enough to live comfortably in documentation, config files and command lines.
Enquiries welcome.