I'm having trouble trying to communicate with the port 587 on smtp.gmail.com on Ubuntu only, but the network and firewall teams (FortiGuard, I think), say that this is not a network nor a firewall related problem.
I have 2 virtual servers (separated VMWare ESXi machines) on the same VLAN: one is Windows Server 2016 and another is Ubuntu Server 22.04.
ufw is disabled on Ubuntu (sudo ufw status replies Status: inactive)
Only Windows server is able to connect to smtp.gmail.com port 587.
Is there any way I can find what is blocking this port 587 on Ubuntu? Are there any firewall or blocking application on Ubuntu Server 22.04 default installation, besides ufw?
Tests on Ubuntu
telnet smtp.gmail.com 587:
Trying 142.251.0.108...
Trying 2800:3f0:4003:c08::6c...
telnet: Unable to connect to remote host: Network is unreachable
telnet -4 smtp.gmail.com 587:
Trying 142.251.0.108...
telnet: Unable to connect to remote host: Connection timed out
sudo nmap smtp.gmail.com
Starting Nmap 7.80 ( https://nmap.org ) at 2023-07-12 18:09 -03
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.30 seconds
sudo nmap -Pn smtp.gmail.com:
Starting Nmap 7.80 ( https://nmap.org ) at 2023-07-12 18:10 -03
Nmap scan report for smtp.gmail.com (142.251.0.109)
Host is up (0.0027s latency).
Other addresses for smtp.gmail.com (not scanned): 2800:3f0:4003:c08::6d
rDNS record for 142.251.0.109: cj-in-f109.1e100.net
Not shown: 997 filtered ports
PORT STATE SERVICE
21/tcp open ftp
113/tcp closed ident
8010/tcp open xmpp
sudo nmap -p 587 -Pn --traceroute smtp.gmail.com:
Starting Nmap 7.80 ( https://nmap.org ) at 2023-07-12 13:50 -03
Nmap scan report for smtp.gmail.com (142.251.0.108)
Host is up.
Other addresses for smtp.gmail.com (not scanned): 2800:3f0:4003:c08::6d
rDNS record for 142.251.0.108: cj-in-f108.1e100.net
PORT STATE SERVICE
587/tcp filtered submission
TRACEROUTE (using proto 1/icmp)
HOP RTT ADDRESS
1 ... 30
Nmap done: 1 IP address (1 host up) scanned in 11.21 seconds
netstat -an:
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:9000 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:33060 0.0.0.0:* LISTEN
tcp 0 0 10.2.40.38:43550 91.189.91.38:80 ESTABLISHED
tcp 0 0 10.2.40.38:56474 185.125.190.75:443 TIME_WAIT
tcp 0 0 10.2.40.38:41044 10.2.40.88:445 ESTABLISHED
tcp 1 0 10.2.40.38:55294 185.125.190.52:443 CLOSE_WAIT
tcp 0 0 127.0.0.1:9000 127.0.0.1:47832 TIME_WAIT
tcp 0 0 10.2.40.38:41222 54.217.10.153:443 TIME_WAIT
tcp 0 0 10.2.40.38:22 10.2.40.66:27284 ESTABLISHED
tcp6 0 0 :::3306 :::* LISTEN
tcp6 0 0 :::80 :::* LISTEN
tcp6 0 0 :::22 :::* LISTEN
tcp6 0 0 :::443 :::* LISTEN
tcp6 0 0 10.2.40.38:443 10.2.40.67:55043 ESTABLISHED
tcp6 0 0 10.2.40.38:443 10.2.40.67:55046 ESTABLISHED
tcp6 0 0 10.2.40.38:443 10.2.40.67:55044 ESTABLISHED
tcp6 0 0 10.2.40.38:443 10.2.40.67:55042 ESTABLISHED
tcp6 0 0 10.2.40.38:443 10.2.40.67:55047 ESTABLISHED
tcp6 0 0 10.2.40.38:443 10.2.40.67:55045 ESTABLISHED
udp 0 0 127.0.0.53:53 0.0.0.0:*
raw6 0 0 :::58 :::* 7
cat /etc/netplan/00-installer-config.yaml:
# This is the network config written by 'subiquity'
network:
version: 2
ethernets:
ens160:
addresses:
- 10.2.40.38/27
routes:
- to: default
via: 10.2.40.33
nameservers:
addresses:
- 10.2.40.62
- 10.2.40.36
search:
- company.local
ip a:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens160: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:29:46:0c:7f:a4 brd ff:ff:ff:ff:ff:ff
altname enp3s0
inet 10.2.40.38/27 brd 10.2.40.63 scope global ens160
valid_lft forever preferred_lft forever
inet6 fe80::29ff:fe46:20c:7fa4/64 scope link
valid_lft forever preferred_lft forever
(Edit to add) Also tested all firewalls status I could think of:
sudo ufw status:
Status: inactive
sudo iptables -L:
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
sudo nft list ruleset
table ip filter {
chain INPUT {
type filter hook input priority filter; policy accept;
}
chain FORWARD {
type filter hook forward priority filter; policy accept;
}
chain OUTPUT {
type filter hook output priority filter; policy accept;
}
}
sudo firewall-cmd --version:
sudo: firewall-cmd: command not found
Tests on Windows
telnet smtp.gmail.com 587:
220 smtp.gmail.com ESMTP n11-20020a0568080a0b00b003a1f444307esm2174022oij.58 - gsmtp
nmap smtp.gmail.com (Using Nmap Zenmap GUI):
Starting Nmap 7.94 ( https://nmap.org ) at 2023-07-12 18:15
Nmap scan report for smtp.gmail.com (142.251.0.109)
Host is up (0.029s latency).
rDNS record for 142.251.0.109: cj-in-f109.1e100.net
Not shown: 991 filtered tcp ports (no-response)
PORT STATE SERVICE
21/tcp open ftp
25/tcp open smtp
113/tcp closed ident
465/tcp open smtps
587/tcp open submission
993/tcp open imaps
995/tcp open pop3s
8008/tcp open http
8010/tcp open xmpp
Nmap done: 1 IP address (1 host up) scanned in 6.72 seconds
nmap -p 587 -Pn --traceroute smtp.gmail.com (Using Nmap Zenmap GUI):
Starting Nmap 7.94 ( https://nmap.org ) at 2023-07-12 13:57
Nmap scan report for smtp.gmail.com (142.251.0.108)
Host is up (0.058s latency).
rDNS record for 142.251.0.108: cj-in-f108.1e100.net
PORT STATE SERVICE
587/tcp open submission
TRACEROUTE (using port 587/tcp)
HOP RTT ADDRESS
1 1.00 ms 10.2.40.61
2 3.00 ms 10.2.40.6
3 13.00 ms 186.238.173.105
4 15.00 ms 186.201.241.153
5 14.00 ms 192.168.5.2
6 14.00 ms 192.168.5.2
7 14.00 ms 192.168.40.2
8 13.00 ms 192.168.40.2
9 14.00 ms 192.168.40.4
10 15.00 ms 187-51-216-237.customer.tdatabrasil.net.br (187.51.216.237)
11 ... 13
14 22.00 ms 108.170.245.141
15 21.00 ms 108.170.245.173
16 51.00 ms 209.85.251.92
17 50.00 ms 209.85.251.92
18 91.00 ms 172.253.64.37
19 70.00 ms 172.253.51.250
20 ... 26
27 15.00 ms cj-in-f108.1e100.net (142.251.0.108)
Nmap done: 1 IP address (1 host up) scanned in 3.51 seconds
ipconfig /all:
Windows IP Configuration
Host Name . . . . . . . . . . . . : WP-SERVER
Primary Dns Suffix . . . . . . . : company.local
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : company.local
Ethernet adapter Ethernet0:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) 82574L Gigabit Network Connection
Physical Address. . . . . . . . . : 00-0C-29-00-85-70
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::e044:c9c3:a574:7f39%2(Preferred)
IPv4 Address. . . . . . . . . . . : 10.2.40.52(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.224
Default Gateway . . . . . . . . . : 10.2.40.33
DHCPv6 IAID . . . . . . . . . . . : 520228888
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-17-1C-CC-CF-00-1F-29-00-85-C9
DNS Servers . . . . . . . . . . . : 10.2.40.62
10.2.40.36
NetBIOS over Tcpip. . . . . . . . : Enabled
