Well, if you mean that you need an email service to blast out emails to 1,000 subscribers, look into MailChimp as they have a free version for a small number of emails. Not sure what the limit is, however. You can also check out Constant Contact and phplist as they have free programs for a small number of subscriber emails. BTW, I use phplist for $5 per quarter and it allows for up to 3,000 or 4,000 emails subscribers, I believe.
From the wording I think he wants to create 1000 email accounts. It's not worth the hassle of creating free accounts - just buy a domain, or use an existing one, and create the pop3 accounts. Any business that has 1000 employees should be able to justify a small outlay to let staff communicate.
I cannot believe that a business has gotten near or to 1,000 employees using free accounts. There must be another reason. But, like you said, just use a pop3 account with any domain you own.