What is "the message" that Step 12 says we are to try to carry to others?

If you think the last sentence is not quite accurate, and that it should say other alcoholics or other addicts, then you're not a member of Al-Anon. Al-Anons make a commitment to carry the message to others -- all others.

If we are members of (for example) AA, then we are told more or less from the beginning of our membership of AA that carrying the message means working with other drunks -- drunks who want to stop drinking, but have no idea how to do this. The treatment of Step 12 in the AA Big Book reflects this: it offers a very comprehensive treatment of how to meet these drunks, how to gain their confidence, how to help them in their early days, and so forth. The Big Book was written within a few years of the discovery that a recovering alcoholic could only stay sober if she attempted to take what she had learned to others, and the excitement of that discovery permeates its treatment of Step 12.

But when we have been in our respective fellowships for some time, and particularly if we have learned to take very seriously the actions recommended in Steps 10 and 11, something seems to shift in our understanding of the message in Step 12. We begin to suspect that this message has as much to do with a spiritual awakening as it does with stopping over-eating or gambling, drinking or drugging. Having had a spiritual awakening as the result of these Steps, we tried to carry this message .... It really does look as though the message is that recovery is actually about waking up to a spiritual reality.

But "obviously you cannot transmit something you haven't got." We can tell the unrecovered addict about NA and take him to a meeting; Chuck Chamberlain in A New Pair of Glasses calls this "carrying the [addict] to the message." But in order to carry the true message of Step 12, we must have "woken up" ourselves on the basis of daily, dedicated practice of Steps 10 and 11. And that is sufficiently rare that -- as we grow in the last three Steps -- we may well find that we end up carrying the message to our fellows who have been in Program for many, many years.