Inbound email from specific servers gets rejected/blocked. In mail client following message appears:
An error occurred sending mail: Unable to establish a secure link with SMTP server mail.solarnex.com using STARTTLS since it doesn't advertise that feature. Switch off STARTTLS for that server or contact your service provider.
/usr/local/psa/var/log/maillog file there are following messages:
localhost postfix/smtpd: NOQUEUE: reject: RCPT from mail.server: 554 5.7.1 Service unavailable; Client host [220.127.116.11] blocked using zen.dnsbl; http://www.spamhaus.org/query/bl?ip=18.104.22.168; from=<firstname.lastname@example.org> to=<email@example.com> proto=ESMTP helo=<mail.server>
localhost /usr/lib64/plesk-9.0/psa-pc-remote: Message aborted.
The IP-address of sending server is listed in spam black lists.
Either delete blocking spam list server from Plesk in Tools & Settings > Mail Server Settings > Switch on spam protection based on DNS blackhole lists > DNS zones for DNSBL service or check more information in the URL provided at
The spam blacklist tool may also be defined in
/etc/postfix/main.cf, for example: