quick whois search:

DOMAIN INFORMATION
Domain:shutterstockmail.com
Registrar:MARKMONITOR INC.
Registration Date:2007-05-09
Expiration Date:2019-05-09
Updated Date:2013-04-16
Status:clientDeleteProhibited
clientTransferProhibited
clientUpdateProhibited
Name Servers:ns1.responsys.net
ns2.responsys.net

REGISTRANT CONTACT
Name:Domain Administrator
Organization:Shutterstock, Inc.
Street:Empire State Building, 350 Fifth Avenue, 21st Floor
City:New York
State:New York
Postal Code:10118
Country:US
Phone:+1.6464194452
Fax:+1.2122422492
Email:[email protected]

ADMINISTRATIVE CONTACT
Name:Domain Administrator
Organization:Shutterstock, Inc.
Street:Empire State Building, 350 Fifth Avenue, 21st Floor
City:New York
State:New York
Postal Code:10118
Country:US
Phone:+1.6464194452
Fax:+1.2122422492
Email:[email protected]

Looks legit to me. Plus, they don't ask for your password...only your email.

So here's the feedback for them: they need to do a better job keeping their contributor site open.  Already twice this past week, the site went down.