mystified by mailto address

[Simon Burton]

Hi all,
Been trying to contact this guy:
mailto:overcode+sdlgc at overcode.net
and have tried all kinds of combinations.
Is the '+' just a space? I don't think sylpheed
is handling the space (just dropping the first word).
Any ideas? He has other mailto addresses but
they all do this '+' thing:
http://isengard.overcode.net/~overcode/

thanks alot,
Simon Burton.