This post has NOT been accepted by the mailing list yet.

[gta_admin]

What does this mean and how do I fix it?

"This post has NOT been accepted by the mailing list yet. "

[GregChapman]

What it says!

It means you have posted to a Nabble archive of a mail list run on another server.

In order for the post to be accepted by the mail list itself you need to be a subscriber there.

Registering and posting on Nabble's archive, does NOT subscribe you to the mail list, so when Nabble forwards your Nabble post to the mail list server that server will not accept your post as you are not a subscriber there.

You should find a link in header of the archive that gives an explanation of this and provides a link enabling you to subscribe to the mail list.