can you elaborate a bit more on what you are doing?  are you setting the forum email address?  alternate user address?  keep in mind, all must exist… or is this the mail server you are trying to set???

and you reference an error message but never say what the message says…

Here is a screen shot http://screencast.com/t/xLzq00om0

I’m trying to set it up so I can reply to a post from: marketingdenforum@gmail.com 

Here is the errors message: 

Delivery to the following recipient failed permanently:

     seth@marketingdenforumgmail.com

Technical details of permanent failure:
DNS Error: Domain name not found

—– Original message —–

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=20120113;
        h=mime-version:x-received:in-reply-to:references:date:message-id
         :subject:from:to:content-type;
        bh=ra0wggv6ySkajeXHf3a6Whk4WJO69ZPuc+kR7AygpgU=;
        b=awGPh4luxlI3B+jB4WJY4nmrGxwinuZpreDAuJNSWUPqCEi12201vj1vvuHxDTZC8t
         OrDfwzPLT9rBNRfLYSO2iVPeO3kYa15KbnJMczTD6CJZVwvdzhlno854OPfg+3FNa1mI
         ZuMyJWlc8L0CxgAt9e0lmsqfi+bq196QR4HDj+C+92hu36jy3UdLmEis/QB7WkmsQ+sC
         bp7yP2ul2eiEQnFfOAVmm8/UcsZGPB29qf/x4OFMyFbXJcyTeNa3MBVZkLb9Azjoz2dn
         li5Dnw47mCKgNYQEikyalx/GnziIhEoX5XiqXljsbyXhr3OTsz2Gl4wppDxmU56UPNB5
         2ACw==
MIME-Version: 1.0
X-Received: by 10.180.14.166 with SMTP id q6mr8576049wic.22.1360201919158;
 Wed, 06 Feb 2013 17:51:59 -0800 (PST)
Received: by 10.194.34.67 with HTTP; Wed, 6 Feb 2013 17:51:59 -0800 (PST)
In-Reply-To: <7b2e94466832de7977e46daf2d04a4de@marketingden.net>
References: <7b2e94466832de7977e46daf2d04a4de@marketingden.net>
Date: Wed, 6 Feb 2013 20:51:59 -0500
Message-ID: <CANbSPZ321GAe-SmRnzLLDAnwisQO9yU_RoJP0ZSyk9tbAPz+bg@mail.gmail.com>
Subject: Re: Forum Post – Marketing Den: [Newbie looking to make more money online]
From: seth riley <marketingdenforum@gmail.com>
To: Marketing Den Member <seth@marketingdenforumgmail.com>
Content-Type: multipart/alternative; boundary=f46d04138cb136db4e04d518b066

so what are you trying to do???  that admin panel section does not have much to do with post by email…  and what you have would be filled in wrong…  senders name is what you want display for the sender, ie Seth Riley…  email from name would be the account of the email…  ie seth…  both the default %% stuff would be fine…  the domain name would be just the domain, not the whole email address… ie marketingden.net…

but this topic is called post by email…  you have not filled in the post by email stuff in the lower left… and have you created and configured email addresses for each forum you want to have this pbe capability?

Mr Papa said
so what are you trying to do???  that admin panel section does not have much to do with post by email…  and what you have would be filled in wrong…  senders name is what you want display for the sender, ie Seth Riley…  email from name would be the account of the email…  ie seth…  both the default %% stuff would be fine…  the domain name would be just the domain, not the whole email address… ie marketingden.net…

I was hopping to be able to reply to any forum topic from my gmail account. It would make it easier for me to reply to my members while I was on the road using my iphone. 

Mr Papa said

but this topic is called post by email…  you have not filled in the post by email stuff in the lower left… and have you created and configured email addresses for each forum you want to have this pbe capability?

No I haven’t done any of that. I guess I didn’t understand how to go about setting it up properly. 

I think with the guideline you are describing above I have a little better understanding of what I need to do.

Questions? How would I go about creating email address for each forum? That confuses me a little because I am not sure if you are talking about me creating an email address’s from my Cpanel for each forum or if I am suppose to go about it a different way.

replying (or creating topics) from an external email is exactly what the post by email plugin is for… but you have to configure it…

have you read:  http://codex.simple-press.com/codex/plugins/our-plugins/available-plugins/plugin-post-by-email/