In case of problems here's a list of all HORDE sites:
dr. Jones, Homebase, Lab, Bitbase, Vega, Louiz.
And here's some other (older, IMP only) sites
(remember to select your own organisation when logging in...!):
dr. Jones, Homebase, Lab, Bitbase, A-host, Macvaerk.

Additionally, here's a few alternative webmail programs
(less secure, but might work better in some situations):
NOCC and AeroMail (dr. Jones/Homebase).