Sending mail from PHP - is the error at my end, or the Mail Server's?

Question

I'm trying to send email via SMTP from my PHP script, running via CodeIgniter.

See below for the debug output. Is this indicative of a problem at my end with PHP (Unable to send email using PHP SMTP) or at their end (hello: 250-parrot.email-provider.co.uk - which would imply to me it has connected to their server, as the actual SMTP server I entered was mail2.email-provider.co.uk, so it seems to connect and redirect to this parrot thing).

My SMTP details I have confirmed to be correct, but it still says it fails to authenticate the password - even though this same password works in my native mail clients.

I've changed my site name and the provider's name (I didn't want to name-and-shame if it was my fault!):

220 parrot.email-provider.co.uk ESMTP Postfix 
hello: 250-parrot.email-provider.co.uk
250-PIPELINING
250-SIZE 512000000
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN CRAM-MD5 DIGEST-MD5
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
Failed to authenticate password. Error: 535 5.7.8 Error: authentication failed: UGFzc3dvcmQ6 
from: 250 2.1.0 Ok
to: 554 5.7.1 : Relay access denied
The following SMTP error was encountered: 554 5.7.1 : Relay access denied 
to: 554 5.7.1 : Relay access denied
The following SMTP error was encountered: 554 5.7.1 : Relay access denied 
to: 554 5.7.1 : Relay access denied
The following SMTP error was encountered: 554 5.7.1 : Relay access denied 
data: 554 5.5.1 Error: no valid recipients
The following SMTP error was encountered: 554 5.5.1 Error: no valid recipients 
221 2.7.0 Error: I can break rules, too. Goodbye. 
The following SMTP error was encountered: 221 2.7.0 Error: I can break rules, too. Goodbye. 
Unable to send email using PHP SMTP. Your server might not be configured to send mail using this method.
User-Agent: CodeIgniter
Date: Wed, 7 Dec 2011 13:30:16 +0000
From: "Mysite.com" 
Return-Path: 
To: [email protected]
Cc: [email protected]
Subject: =?utf-8?Q?The_Subject?=
Reply-To: "[email protected]" 
X-Sender: [email protected]
X-Mailer: CodeIgniter
X-Priority: 3 (Normal)
Message-ID: <[email protected]>
Mime-Version: 1.0

Answer 1

Can be:

1. Wrong password.

2. Login method not allowed/recognized by server.