gistfile1.txt

---- dig from the mail relay system
# dig mx guilford.com +short
10 smtp.notes.na.collabserv.com.

# dig smtp.notes.na.collabserv.com +short
158.85.210.111
158.85.210.104
158.85.210.113
192.155.248.93
158.85.210.110
192.155.248.67
158.85.210.120
192.155.248.72
192.155.248.82
158.85.210.103
192.155.248.68
158.85.210.112
158.85.176.4
158.85.210.119
192.155.248.71
192.155.248.75
192.155.248.73
192.155.248.70
158.85.210.114
158.85.210.108
158.85.176.6
158.85.210.109
192.155.248.90
192.155.248.81
192.155.248.66
192.155.248.91
158.85.176.5
192.155.248.74

---- Tcpdump while postfix is trying to resolve the MX record
# tcpdump -vvv -s 0 -l -n port 53 | grep guilford
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
    172.22.130.242.35796 > 10.0.2.77.53: [bad udp cksum 0x3b8d -> 0xe316!] 50686+ MX? guilford.com. (30)
    10.0.2.77.53 > 172.22.130.242.35796: [udp sum ok] 50686| q: MX? guilford.com. 1/0/27 guilford.com. [2h37m37s] MX smtp.notes.na.collabserv.com. 10 ar: smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.104, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.70, smtp.notes.na.collabserv.com. [3m18s] A 158.85.176.5, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.82, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.120, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.112, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.103, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.81, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.91, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.110, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.68, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.72, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.113, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.73, smtp.notes.na.collabserv.com. [3m18s] A 158.85.176.6, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.90, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.93, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.74, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.111, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.66, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.75, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.114, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.67, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.108, smtp.notes.na.collabserv.com. [3m18s] A 192.155.248.71, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.119, smtp.notes.na.collabserv.com. [3m18s] A 158.85.210.109 (503)