Basic postfix setup... can't start smtp-tunnel - ssh problem

I'm setting up my first linode and everything has gone well so far. But I just got to basic email configuration, and decided to go with the most basic postfix setup guide at ~~[http://library.linode.com/email/postfix/gateway-ubuntu-10.10-maverick" target="_blank">](http://library.linode.com/email/postfix … 0-maverick">http://library.linode.com/email/postfix/gateway-ubuntu-10.10-maverick]( . Note that it's for 10.10 and I'm running Ubuntu 11.04. But I doubt that is the problem here.

In the guide, I got most of the way through, to where I've created the script /opt/smtp-tunnel and customized the $remoteuser and $remotehost lines as suggested. After saving that, I followed the instructions to make /opt/smtp-tunnel executable and start it up. That resulted in one of those questions you get the first time you SSH to a new location (authenticity can't be established, are you sure you want to continue? yes… permanently added 'bcdev.info, 96.126.97.84' (ECDSA) to the list of known hosts." Permission denied (publickey).

Here are the relevant lines that I customized in /opt/smtp-tunnel:

$remote_user = "foo";

$remote_host = "bcdev.info";

foo (altered in this post for safety) is the account on my linode that I use for most things instead of root.

bcdev.info is my domain.

My only guess about what's wrong so far is that maybe I was supposed to put www.bcdev.info there instead? The docs were kind of fuzzy about the need to use my FQDN and whether that includes the www subdomain or not.

Other pertinent info:

in /etc/postfix/main.cf:

myhostname = bcdev.info

Also, what I entered for "system mail name", the single option that came up in the config screen that auto-runs when you apt-get install postfix, was: bcdev.info.

This is my first time through this and don't have any better idea of where I went wrong. Obviously something to do with SSH keys, but I thought I already had those set up, having already successfully installed Postgresql and system users for it, etc.