First here is a 3KB that may come in handy trying to troubleshoot OSN . You can do a network trace on SMTP or you can enable ( short term only ) nbxinetnot0 in cfg logging on the NBX . This will tell you in our NBoss log who is using osn . Just remember not to leave it on for extended periods as it will take a lot of memory out of the system and can bring the site down after a while , if left on plus fill up your NBoss logs with a lot of info as well . so use it sparingly

NBX - Troubleshooting offsite email notification message delivery
Solution ID - 2.0.88348627.3458295

Goals:




Symptoms:

Troubleshooting offsite Email notification and message delivery




Send off-site Email notification



Unable to send Email messages using off-site notification


Email not working



Not receiving off-site Email





Changes:




Facts:

NBX 100
SuperStack 3 NBX
Off-site notification
Email notification
APX Voice Messaging
NBX messaging
DNS
SMTP domain name
Primary DNS
Secondary DNS
Host Name
MTA
SMTP Client
NAT


Causes:

SMTP Domain Name field is incorrect
NBX not able to perform DNS NSLOOKUP of destination email server
NBX not able to establish an SMTP Telnet (port 25) connection
Destination email server denying NBX connection
Firewall preventing Telnet port 25 requests
More than one email address per Attempt line in User Settings
DNS configuration is incorrect or unreachable
In early R4_0_X software, off-site email cannot be sent to AOL email accounts. This is fixed in the later code releases - R4.1.66 and higher


Fixes:

Here's how the NBX sends off-site email (NAT is fully supported for off-site email messaging):

1 - In NetSet it must be enabled in System-Wide, in CoS, and on each User before it will work
2 - NCP performs an MX record lookup using DNS server IP information to return a valid TCP/IP address for each message being sent
3 - NCP acts as an MTA (Message Transfer Agent) - will directly contact each destination mail server for local delivery
4 - NCP establishes a TCP socket to the resolved TCP/IP address on SMTP port 25
5 - NCP must be able to open a TCP session to the resolved IP address of each destination email server
6 - Each destination server the NBX is sending email to may be configured for a rule base and based on certain criteria my reject an email or attachment that other email servers accept. For example, some email servers may at first accept the email from the NBX, and after the NBX gets an OK and disconnects, the destination email server may do one of several validations, including check for a valid sending address. Does NBX@your-smtp-domain-name exist? The NBX will use this as the sending address, which may not itself be a valid return address. This may be only one of many customized rules that destination servers can do, even after accepting an NBX email, that prevents delivery to the recipient.
The SMTP Domain Name should validate to YOUR NCP public IP being used. If you do not own a registered domain, you should put your ISP's domain name here in the form "xxxxx.com"

TROUBLESHOOTING TIPS:
- A packet trace will reveal in MINUTES whether the NBX is able to contact the intended mail server, and whether the message was accepted. There are 4 main reasons why a message will not deliver and possible reasons:

1 - NBX is not trying to send the message
(off-site notify not fully enabled at system, group, and user levels, user has syntax error for the email address - only one address per line - no commas or multi sends per line)

2 - NBX is unable to resolve the IP address of the destination email server as typed in the user settings for delivery (DNS server info wrong, DNS server unavailable, router/firewall preventing this connection)
** Have the Network Admin confirm that the DNS IP address set in NetSet is valid, reachable, and will return an MX record with the IP address (not just the MX name), for the target or test email account domain name. This step is critical so that the NBX will know the IP address of the email server it must reach for every external email address it must contact.

3 - NBX is unable to establish a TCP connection on port 25 directly to the destination email server
(Destination email server down, firewall/router has port 25 blocked, destination email server is In House and router/firewall is preventing looped connection to the public side of the in-house private DNS or MAIL server)

4 - Destination email server, after connection, either rejects the message, or accepts it but may not deliver it due to post-send validation rules they have set up.
(TCP mail connection is poor; Telnet session timed out, SMTP domain name did not verify, various errors reported by destination email server within the TCP connection - must do a packet trace to see these errors) MANUALLY you may try to do the steps that the NBX does, using a PC on the same sub-net as the NBX to catch problems listed above. Below is a basic outline of what to do, not detailed. Perform these steps at a PC's DOS prompt that can do NSLOOKUP (Win 2000, Win NT, etc). ** Be sure that the PC you are testing from is on the same subnet as the NCP, and, that the DNS IP address shown on the PC with "ipconfig /all" is the same DNS server IP as has been set in NetSet, to ensure you are testing just as the NBX would be sending.

In this example, we're trying to send an off-site email to "Jerry@Home.Com"

- Perform an NSLOOKUP of the destination domain. Windows NT and 2000 support NSLOOKUP.
From the DOS prompt type:
NSLOOKUP
> set type = MX
> home.com (this is an example)

home.com MX preference = 50, mail exchanger = mx-rr.home.com
(there may be more listings. Often, in the server name list, the mail exchanger IP address may be defined. If it is, the NCP will have the mail server IP address and not need to do any further DNS lookup.)

- now resolve the IP address for the mx-rr.home.com mail server after exiting NSLOOKUP by typing EXIT

- at the C:\ prompt type
NSLOOKUP
> mx-rr.home.com (the name of the mail server you are trying to connect to. Do NOT set type to mx this time)

- you will get at least 1 IP address back for that server, maybe more:
65.10.73.243, 24.0.95.20, 24.0.95.21, 65.10.73.242

- Now try to connect using the PC directly to the destination email server to test tcp port 25 on your LAN

- type "telnet 65.10.73.243 25" at the DOS prompt. Don't forget the 'space 25' after the IP address to indicate SMTP connection

- You should get a response directly from the destination email server, and you will be in an interactive TCP mail session at this point. This basically tries to prove correct DNS, NSLOOKUP, and router/firewall configuration to allow the NBX to directly establish an email connection to an off-site mail server. This does not mean the message will deliver, there may be an error that comes up during the sending of the message, or the NBX setting may be different from the PC you are testing on. But if you got this far on a PC on the same sub-net as the NCP, the NCP with correct configuration should be able to do the same and send email. If you get this far but still NO email will deliver, even when trying different off-site email domain addresses (send to several different email addresses at different ISP mail providers) then a packet trace will be necessary. The good news is a packet trace will be able to quickly indicate the point of failure, or prove the NBX successfully delivers the message but the destination server is not delivering it after receipt for post-processing reasons.

- If an Office Connect Firewall (5x1 Models)is used with NAT enabled, click [here] for solution. Upgrade the firmware to 6.03a or later on the Office Connect Product to address an issue with SMTP. (Office Connect 25 Firewall has no issues)


Notes:




Product(s):

NBX


Sub Product(s):

NBX 100, SuperStack 3 NBX



Date Article Modified: 2004-10-08





-------------------------
Rich O'Connor
3Com Enterprise Support