DPopper is a 'dummy' POP3 server. It can be used to handle hoards of marauding customers while your real POP3 server is having a bad day. It will appear to authenticate anybody, and will accept any password they offer. It will also tell them they have no new mail, hence provides the backend for 'transparently' failing POP3 servers. (Not written here, but seems to have disappeared from http://tdx.com/software along with their site. Mirrored here because we found it useful with TinyDynDNS.) DPopper is licensed under "the Original BSD License". That's the one with the "advertising clause".
No support is offered for DPopper. I didn't write it (Karl Pielorz did and was kind enough to release it), and I am not a C programmer. I'm only offering this code because it was helpful to me, and the license allows me to distribute it, and the original source is "down for maintenance." That doesn't mean you can't ask on the mailing list, it just means I'm not promising that the code will work for you, or that I'm capable of helping you get it working.
View the current: README • License (Original BSD)
You'll need a C compiler to compile this program.