I'll leave it to you to choose the moral that best suits your beliefs and lifestyle.
Here's another true story: An employee at a small company was severely allergic to perfumes and other fragrances. She sent flame mail to the entire organization demanding that everyone immediately cease using all scented products. The next day, someone sprayed perfume all over her office.
Note that Netiquette condones neither the flame mail nor the perfume-spraying. The point, however, is that the arrogance and rude tone of the mail provoked the extreme reaction. The fact that you have the capability to send mail instantaneously to large groups of people doesn't make it a good idea. Completely apart from the ethics of the situations described here, you need to be really careful if you have access to an all-company mailing list.
Some companies don't make it so easy for their employees to send mail to everyone in the organization. Where I used to work, one person (for awhile it was me) had to screen every message that was sent out to all employees. We needed to do that because our system didn't let users prioritize their messages, and people got very irritated when they received messages that were of no interest or relevance to them. The system worked fairly well, although there was some cost in terms of my time and lost opportunities for communication.
Other companies have mail areas called "Junk Mail" or "Fourth Class Mail" that employees can use for classified ads, requests for general information, etc. Mail with these designations is usually separated from normal person-to-person mail, so busy people aren't bothered by it. If your company offers this benefit, use it -- but follow the organization's rules and check everything twice before you send it out.
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