SELinux and sending mail via HTTPD - CentOS 7

Use this SELinux command to give the Apache process to use sendmail:

#sudo setsebool -p httpd_can_sendmail 1

Monitor DNS lookup

# tcpdump -i eth0 port 53
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
10:48:15.324300 IP client.63533 > dns-server.domain: 17904+ PTR? 1.0.0.127.in-addr.arpa. (40)
10:48:15.324848 IP dns-server.domain > client.63533: 17904* 1/1/2 PTR localhost. (121)
10:48:15.325137 IP client.50547 > dns-server.domain: 49520+ AAAA? localhost. (27)
10:48:15.325293 IP client.43181 > dns-server.domain: 25134+ PTR? xx.x.xxx.xxx.in-addr.arpa. (43)
10:48:15.325643 IP dns-server.domain > client.50547: 49520* 1/1/1 AAAA ::1 (85)
10:48:15.325903 IP dns-server.domain > client.43181: 25134* 1/3/6 PTR dns-server. (268)
10:48:19.565837 IP client.25663 > dns-server.domain: 43756+ AAAA? client. (42)
10:48:19.566389 IP dns-server.domain > client.25663: 43756 NXDomain* 0/1/0 (93)
10:48:19.566497 IP client.64053 > dns-server.domain: 55198+ AAAA? client. (40)
10:48:19.567026 IP dns-server.domain > client.64053: 55198* 0/1/0 (91)
10:48:19.567086 IP client.49399 > dns-server.domain: 1076+ AAAA? client. (37)
10:48:19.567600 IP dns-server.domain > client.49399: 1076 NXDomain* 0/1/0 (88)
10:48:19.567656 IP client.24922 > dns-server.domain: 50409+ AAAA? client. (26)
10:48:19.568080 IP dns-server.domain > client.24922: 50409 NXDomain 0/1/0 (101)
10:53:15.248429 IP client.17122 > dns-server.domain: 45962+ PTR? 1.0.0.127.in-addr.arpa. (40)
10:53:15.248968 IP dns-server.domain > client.17122: 45962* 1/1/2 PTR localhost. (121)
10:53:15.249332 IP client.17597 > dns-server.domain: 59594+ AAAA? localhost. (27)
10:53:15.249819 IP dns-server.domain > client.17597: 59594* 1/1/1 AAAA ::1 (85)
10:53:19.590980 IP client.52610 > dns-server.domain: 39707+ AAAA? client. (42)
10:53:19.591525 IP dns-server.domain > client.52610: 39707 NXDomain* 0/1/0 (93)
10:53:19.591683 IP client.32529 > dns-server.domain: 23733+ AAAA? client. (40)
10:53:19.592180 IP dns-server.domain > client.32529: 23733* 0/1/0 (91)