I see that your second attempt has worked fine (message subject "Re: PDO or Mysqli?"):
http://n4.nabble.com/user/UserNodes.jtp?user=54955&node=634137So I think you should just delete the old pending messages.
David Muir wrote
Is there a way to tell Nabble to accept emails from alternate addresses?
You should get the subscription address for your alternate email. To do this, log out and go to the forum you want to post to. Then click on "Options > Post by email" and enter your email. Nabble will send an email to you with the address you should use to post new topics.