Postfix rejecting mail from authenticated clients

I am trying to configure Postfix so that it would accept mail from authenticated clients outside $mynetworks.

When I try to send a test email from my iPhone, which is configured to use port 25, SSL and password authentication, the mail gets rejected by Postfix. I get the following in /var/log/mail.info:

Oct 25 17:41:35 mailhost postfix/smtpd[6136]: warning: 212.183.x.x:
hostname host212-183-x-x.uk.access.vodafone.net verification
failed: Name or service not known

Oct 25 17:41:35 mailhost
postfix/smtpd[6136]: connect from unknown[212.183.x.x]

Oct 25
17:41:39 mailhost postfix/smtpd[6136]: NOQUEUE: reject: RCPT from
unknown[212.183.x.x]: 554 5.7.1 : Client
host rejected: Access denied; from=<aix@x.com>
to=<aix@x.com> proto=ESMTP helo=<[10.25.x.x]>

Oct 25
17:41:39 mailhost postfix/smtpd[6136]: disconnect from
unknown[212.183.x.x]

Here are all my main.cf settings that have to do with SASL/TLS:

smtpd_tls_cert_file = /etc/ssl/certs/ssl-mail.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-mail.key
smtpd_use_tls = yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_sasl_auth_enable = yes
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/dovecot-auth
smtpd_sasl_authenticated_header = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions = reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_pipelining, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
smtp_use_tls = yes
smtpd_tls_received_header = yes
smtpd_tls_mandatory_protocols = SSLv3, TLSv1
smtpd_tls_mandatory_ciphers = medium
smtpd_tls_auth_only = yes
tls_random_source = dev:/dev/urandom

How do I establish that the session is indeed authenticated?

How do I go about troubleshooting this further?