This is a job for a bulk email service. You definitely don’t want to try to bcc: all your users via a regular email account.
There are dozens of bulk providers out there that let you upload your list, design an email, set the “from” and “reply-to” addresses, and go.
Depending on the size of your list, this might be free or might cost a few bucks. Many providers have a free tier for 1000 to 3000 recipients or messages/month. I like CampaignMonitor for this kind of occasional use, because they offer a pay-per-campaign rate (currently $5/campaign, +.01 per address) that you can use without a monthly subscription.
Note that these bulk emails will also include an “unsubscribe” link. The best you can do is send the emails, and keep the campaign log/report. You can’t force people to receive them.