GNUS with unauthenticated smtp server

[Tory S. Anderson]

I use gnus, specifying outgoing stuff with my .authinfo.gpg 
file. I'm trying to match these settings (intended for 
Thunderbird):

> Outgoing Mail Server (SMTP): gateway.byu.edu

>    Click More Settings.
>    Select the Outgoing Server tab.
>    Do not check My outgoing server (SMTP) requires 
>    authentication.
>    Select the Advanced tab.
>    Outgoing server/port number: 25
>    Check This server requires an encrypted connection (SSL) 
>    Incoming Server

When I use the VPN to make my outgoing eligible, I receive the 
following error:

> gnutls.c: [1] (Emacs) fatal error: An unexpected TLS packet was 
> received.
> gnutls.el: (err=[-15] An unexpected TLS packet was received.) 
> boot: (:priority NORMAL :hostname gateway.byu.edu :loglevel 1 
> :min-prime-bits 256 :trustfiles (/etc/ssl/ca-bundle.pem) 
> :crlfiles nil :keylist nil :verify-flags nil :verify-error nil 
> :callbacks nil)
> gnutls-negotiate: GnuTLS error: #<process smtpmail>, -15

first off, I can't figure out what error -15 is; second, I'm not 
entirely sure how to simulate "Do not check My outgoing server 
(SMTP) requires authentication." (ie how to go unauthenticated 
through my authinfo file). Any help would be much-appreciated!

- Tory