Revert "Fix for multiple ipv4" (#306 #310) (#325)
Revert "Fix for multiple ipv4" (#306 #310) (#325)

This reverts commit e5d14fd0bc79c21e89ebc51ce81e9b31cd1f35d0.
172.0.0.0-172.15.255.255 and 172.32.0.0-172.255.255.255 are valid
external IP addresses. Try PERMIT_DOCKER: network instead.
Narzhan/docker-smtp,tomav/docker-mailserver,keslerm/docker-mailserver,alinmear/docker-mailserver,tomav/docker-mailserver,tomav/docker-mailserver