Problem with postfix, ISPconfig on a Strato vServer

[Been Told]

Hi!
I have the following setup that I recently installed ISPconfig on:
vServer Strato
Debian Etch
ISPconfig 2.2.7
The assumed domain name here is domain.tld
My postfix/main.cf is the following (xxxxx replaces the server name)

Datei: /etc/postfix/main.cf

myhostname = xxxxxxxx.stratoserver.net
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
#mydestination = xxxxxxxx.stratoserver.net, xxxxxxxx.stratoserver.net, localhost.stratoserver.net, localhost
relayhost =
mynetworks = 127.0.0.0/8
mailbox_command =
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
smtpd_sasl_local_domain =
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject _unauth_destination
smtpd_tls_auth_only = no
smtp_use_tls = yes
smtp_tls_note_starttls_offer = yes
smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom
home_mailbox = Maildir/

virtual_maps = hash:/etc/postfix/virtusertable

mydestination = /etc/postfix/local-host-names


The Problem I am having is that when I try to send e-Mail via Outlook, I get the following e-mail back:

Your message did not reach some or all of the intended recipients.

Subject: Wir prüfen
Sent: 02.12.2008 16:35

The following recipient(s) cannot be reached:

'mail@recipient.tld' on 02.12.2008 16:35
554 5.7.1 <mail@recipient.tld>: Relay access denied



And the e-mail doesn't get sent.
When I send an e-mail TO the account, I get the following e-Mail back:


Reporting-MTA: dns; xxxxxxx.stratoserver.net
X-Postfix-Queue-ID: 5A3AD21838A
X-Postfix-Sender: rfc822; mail@recipient.tld
Arrival-Date: Tue, 2 Dec 2008 16:51:02 +0100 (CET)

Final-Recipient: rfc822; web1_test@xxxxxx.stratoserver.net
Original-Recipient: rfc822;paul@domain.tld
Action: failed
Status: 5.4.4
Diagnostic-Code: X-Postfix; Host or domain name not found. Name service error
for name=xxxxxx.stratoserver.net type=A: Host not found


Now, this is only my second server I've ever administered and I may have made a misstake.
On my other server, when ISPconfig asked me what server name and domain I wanted to use, I always used server1 as the server name and an assumed domain.tld the domain.
But on this occasion I used xxxxxx.stratoserver.net instead of server1.domain.tld.

Could that be the cause of the problem?

EDIT:
I have added A records for xxxxx.stratoserver.net, but the problem still exists.

[Been Told]

The relevant error message:
Dec 2 21:15:06 XXXXXXXX courierpop3login: LOGIN, user=web1_email, ip=[::ffff:91.1.11.111]
Dec 2 21:15:06 XXXXXXXX courierpop3login: LOGOUT, user=web1_email, ip=[::ffff:91.1.11.111], top=0, retr=0, rcvd=12, sent=39, time=0
Dec 2 21:15:07 XXXXXXXX postfix/smtpd[9753]: connect from ******.dip.t-dialin.net[91.1.11.111]
Dec 2 21:15:07 XXXXXXXX postfix/smtpd[9753]: NOQUEUE: reject: RCPT from ******.dip.t-dialin.net[91.1.11.111]: 554 5.7.1 <email@domain.tld>: Rela$
Dec 2 21:15:07 XXXXXXXX postfix/smtpd[9753]: disconnect from ******.dip.t-dialin.net[91.1.11.111]

XXXXXXXX is the server name.

[falko]

The Problem I am having is that when I try to send e-Mail via Outlook, I get the following e-mail back:

Your message did not reach some or all of the intended recipients.

Subject: Wir prüfen
Sent: 02.12.2008 16:35

The following recipient(s) cannot be reached:

'mail@recipient.tld' on 02.12.2008 16:35
554 5.7.1 <mail@recipient.tld>: Relay access denied


You must enable "Server requires authentication" in your email client.


When I send an e-mail TO the account, I get the following e-Mail back:


Reporting-MTA: dns; xxxxxxx.stratoserver.net
X-Postfix-Queue-ID: 5A3AD21838A
X-Postfix-Sender: rfc822; mail@recipient.tld
Arrival-Date: Tue, 2 Dec 2008 16:51:02 +0100 (CET)

Final-Recipient: rfc822; web1_test@xxxxxx.stratoserver.net
Original-Recipient: rfc822;paul@domain.tld
Action: failed
Status: 5.4.4
Diagnostic-Code: X-Postfix; Host or domain name not found. Name service error
for name=xxxxxx.stratoserver.net type=A: Host not found


What are the outputs of hostname and hostname -f and what's in /etc/hosts?

[Been Told]

You must enable "Server requires authentication" in your email client.

It was enabled from the start.

What are the outputs of hostname and hostname -f and what's in /etc/hosts?
hostname and hostname -f both return:
hXXXXX.stratoserver.net
/etc/hosts is:

127.0.0.1 localhost.localdomain localhost
85.XXX.XXX.XXX hXXXXX.stratoserver.net hXXXXXX

Thanks for your reply falko. :)

[Been Told]

Looks like the matter is settled. The guy I'm installing the server software for has decided to go with openSUSE and Plesk. Thanks for your help falko. :)