Implement error checking for blacklisted IPs

[oxr463]

[root@ip-172-26-7-166 beatles]# nc -C outlook.com 25
220 DM3NAM03FT051.mail.protection.outlook.com Microsoft ESMTP MAIL Service ready at Fri, 19 Apr 2019 20:03:00 +0000
HELO
250 DM3NAM03FT051.mail.protection.outlook.com Hello [3.211.34.40]
Mail
501 5.5.4 Unrecognized parameter [DM3NAM03FT051.eop-NAM03.prod.protection.outlook.com]
MAIL FROM: noreply@cyberninjas.com
250 2.1.0 Sender OK
RCPT TO: email
550 5.7.1 Service unavailable, Client host [3.211.34.40] blocked using Spamhaus. To request removal from this list see https://www.spamhaus.org/query/ip/[3.211.34.40] (AS16012611) [DM3NAM03FT051.eop-NAM03.prod.protection.outlook.com]

Originally posted by @neverrend in #34 (comment)

Source: CyberNinjas/pam_aad#35