Assigning around here is done by associations and via The Arbiter. Our contact info is available online for fellow officials, schools, ADs, coaches, etc. to see. It's been no problem.
However, we are instructed to confirm the date/time of the game with the AD and our partner by phone. And once in a while, it saves everybody a lot of grief because when game times and locations change, nobody seems remember to contact the officials.
Now as for the spam, that's interesting. Is The Arbiter selling email addresses?