Not that I know of. You can, perhaps, take an existing distribution (for example Tom's root boot disk) and load a pop3 daemon using another floppy.
The biggest problem is the space requirements of the daemon tools and a working kernel + userspace programs to configure stuff.
A 2.88 Mb floppy would bring more possibilities, only not everybody has a 2.88 Mb floppy drive.
Why don't you try Knoppix instead??? :-)