Outlook Express could be used to send out mass emails in the past. However, as with other email programs, it only allows a few now to be sent, something like 30 at one time (to prevent spammers from using it). Iv'e used it to send out a newsletter before that upgrade.
With the older version, you could move all the emails to your draft folder. Then select them all to mail. After that, you could put in the address and then send them. I don't know if this works with the versions that only allow a limited amount of emails to be sent at one time.
I don't know if that will work now.