Thanks, very useful tips.
Regarding searching in googlegroups, if you use author:@companyname.com the results tende to be more specific
I tend to use Rithesh' approach of googling "@companydomain.tld", most of the time in combination with an easily accessible name of a random member of staff. However I do also like the "email * @companydomain.tld" -approach.
Every now and then I come across a company without a straight email-pattern,h forcing me to send trial & error mails to all probable variations. Does that happen to you as well?