How an employer treats inter-office communication can be an important factor in whether employees are singled out for discrimination. Invitations to join a religious gathering or join in a prayer for any reason could easily open the door for unlawful discrimination. The right to observe the religion of your choice, or refrain from joining in a religious observance that does not match your beliefs, is guaranteed in the U.S. Constitution and under New Jersey law. If you are penalized or persecuted for your religious beliefs, your employer is violating the law.
Invitation or order?
It is difficult to be singled out in any setting. Being the only person of a particular creed or religious belief system in a group can be intimidating. Employers can easily violate your rights if they mistake a majority for the entirety. If you are invited to join a Christian prayer group by your boss, will you be made to suffer for choosing to abstain?
Whether the communication is through email or message boards, invitations of a religious nature should be treated like any other non-work related item. If a company allows employees to discuss charity events, social gatherings and other personal matters, a religious message about a prayer group or non-secular gathering may be acceptable. If the company has a strict, business-only philosophy about email and other work communication, a religious email that does not draw a rebuke is problematic.
Accommodation versus normalization
Employers are required to provide reasonable accommodation for sincerely held religious beliefs. That is not the same as choosing a single faith as the norm in the office. You have the right to practice your religion. The employer does not have the right to establish one religion and punish those who have different beliefs.
The failure to accommodate is a violation of employment law, as is discrimination based on your beliefs. If you have been a victim of either, you should speak to an attorney about your rights.