Email addresses in URLS?

Hello. I'm wondering if you can assist with advice regarding
passwords/hiding emails.

basically,

a) a user enters their email address

b) I generate a code for login and generate an email.

c) the email contains the URL to log in

http://website.com/login?code=EMAILADDRESS-GENERATEDCODE

When the person clicks on it, I separate the email address - and
generate a new code - if it matches, they are logged in.

MAIN CONCERN - is if I have an email address in the actual URL, it may
be easier for spammers to pick it up & start spamming the user.. (I'm
not doing the spamming)..

Is that a real or imaginary concern? would the ISPs be spamming folk &
scanning for URLs that pass through their servers for email addresses?

Would a MySQL database be best - to store email addresses & assign a
user number for each email? Then use the user number in the URL?

-- 

Gordon.