1. Virtual Machine: Ubuntu 14.04.1 LTS
  2. I'm using putty to access Ubuntu from my Windows 7 PC.
  3. This Ubuntu machine does not have a registered domain name.
  4. Setting up a local SMTP server on this Ubuntu VM requires a full MTA which requires a registered domain name, which isn't going to happen.
  5. On the Ubuntu VM I'm using the Google name servers of and
  6. For old SMTPServer1, there is a limit if about 100 outgoing emails per day per account/username, and I'm the only one who uses this SMTP username and I don't generate 250 emails every day. I do about 25-30 max on certain days.
  7. I'm using Perl 5.18.2 to talk directly to the SMTP server, so I don't need an MTA.
  8. On my Ubuntu VM, doing nslookup email.abc.com gives me a non-authoritative IP address of the correct IP for the new SMTP server, which is, say

This Ubuntu VM runs on our network and I've been making reports and sending outbound email only via SMTPServer1 for a while now. SMTPServer1 has poor service so I'm changing SMTP servers to an SMTP server internal to our network, something our company runs. When I try to test my connection from Ubuntu to the new SMTP server, I telnet in to the name like this: telnet email.abc.com 2525 because we use a non-standard port for SMTP.

What I get every time is "Trying email.abc.com..." and it just hangs there until I get a timeout error. The same thing happens when I try to telnet directly to the IP address. The other guy running the new (to me) SMTP server claims it's open for my IP of the Ubuntu server and his SMTP server is running.

  1. First, what do I need to check? I'm on my own here, IT doesn't know anything about Ubuntu.
  2. How do I set up my machine, and/or DNS, to access the new SMTP server? I already know how to set up my Perl program to do it, but my test is not working, hence my question.

Thank you!

EDIT: I just added our internal DNS servers to /etc/network/interfaces. The first 2 entries for dns-nameservers are 10.19.* and they are our internal DNS servers. The next 2 entries are Google DNS servers, the last is a OpenDNS server. It now looks like this:

# This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet static address netmask gateway dns-nameservers # See /home/chuck/perl/stuff/setiptable. pre-up iptables-restore < /etc/iptables/rules.v4

After the edit (using sudo nedit /etc/network/interfaces) I did: sudo service network-manager restart. I also edited sudo /etc/resolvconf/resolv.conf.d/base which now has our 2 internal DNS servers first, followed by 2 Google DNS servers, and it now looks like this:

nameserver nameserver nameserver nameserver

After editing I did sudo resolvconf -u.

So then I did ping and nmap. Ping works. Nmap returns this. If someone could help me decipher the nmap output, then I can learn. I don't mind learning. But I'm new at this part. Everyone is at one point.

Starting Nmap 6.40 ( http://nmap.org ) at 2015-06-23 06:39 EDT Nmap scan report for email.abc.com ( Host is up. rDNS record for acmkokisco.gs01.gridserver.com PORT STATE SERVICE 2525/tcp filtered ms-v-worlds

Nmap done: 1 IP address (1 host up) scanned in 2.12 seconds

If I'm doing nmap from my Ubuntu server to the SMTP server, why does it say "filtered"? Did the guy running the SMTP server not allow my Ubuntu IP correctly? I know when you make changes to Ubuntu you sometimes have to restart services. I wonder if he didn't restart the service correctly. I am trying to figure out what to tell him, i.e. if the problem is at my end or his.

Output of nslookup email.abc.com:

Server: Address:

Non-authoritative answer: Name: email.abc.com Address:

Doesn't this mean it used the (Google) DNS server to get the IP? is the IP of my Ubuntu machine, and I'm trying to access the SMTP server from there. Output of tcptraceroute.

$ tcptraceroute email.abc.com 2525 Selected device eth0, address, port 57049 for outgoing packets Tracing the path to email.abc.com ( on TCP port 2525, 30 hops max 1 * * * 2 * * * 3 * * * 4 * * * 5 * * * 6 * * * 7 * * * 8 * * * 9 * * * 10 * * * 11 * * * 12 * * * 13 * * * 14 * * * 15 * * * 16 * * * 17 * * * 18 * * * 19 * * * 20 * * * 21 * * * 22 * * * 23 * * * 24 * * * 25 * * * 26 * * * 27 * * * 28 * * * 29 * * * 30 * * * Destination not reached

  • Please keep it clean on this site. Jun 22, 2015 at 19:02
  • 1
    Can you ping the SMTP server? It sounds like a filter/firewall/access issue to me. If you are allowed to, sudo apt-get install nmap, then nmap -sS -P0 -p 2525 email.abc.com. If it returns the state as "filtered", there's likely a firewall in the way (or you're not in an IP allowed email server config). It should return the state as "open".
    – stevieb
    Jun 22, 2015 at 21:44
  • stevieb: I edited my original post with my answers, because I can format it better there.
    – Bulrush
    Jun 23, 2015 at 10:46

1 Answer 1


First uou should check/rule out being "firewalled out".

You may use tcptraceroute email.abc.com 2525

man tcptraceroute
package tcptraceoute

  • I edited my original post to show nmap output, which shows my IP is being filtered. Is tcptraceroute worth installing? Will it give me more info?
    – Bulrush
    Jun 23, 2015 at 10:55
  • Added output of tcptraceroute to original post.
    – Bulrush
    Jun 23, 2015 at 11:05
  • Could you add tcpraceroute to reachable smtp port on SMTPServer1?
    – AnFi
    Jun 25, 2015 at 8:09

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