[dns-operations] email address in SOA

[Feng He]

Hello,

for the soa record, i.e,
google.com.             43199   IN      SOA     ns1.google.com. 
dns-admin.google.com. 2012113000 7200 1800 1209600 300

Though I know dns-admin.google.com is an email address standing for 
dns-admin at google.com

I have the questions that:

#1 what purpose is this address used for?
#2 if the admin email is foo.bar at gmail.com, then it express as 
foo.bar.gmail.com. Thus how to differ it's foo at bar.gmail.com or 
foo.bar at gmail.com?

Thanks.