400 level GWIA error messages, their causes and resolutions:

(Last modified: 28Jan2005)

This document (10060050) is provided subject to the disclaimer at the end of this document.

goal

fact

Novell GroupWise 5.5

Novell GroupWise Internet Agent (GWIA)

symptom

Error: 420 TCP Write Error

Error: 450 Host Down.

Cannot send to some Internet sites

fix

400 level GWIA error messages, their causes and resolutions:

All of these errors occur only when the GWIA is processing an outbound email.

All 400 level errors result in the GWIA queuing the message to the defer folder, where it will try repeatedly to deliver the mail over a period of 4 days.

420 TCP read error and 420 TCP write error

In a few instances, a corrupt message in the <domain>\gwia\send folder will cause a 420 TCP read error.

In other cases, these messages are caused by a communication problem between the GWIA and another mail host on the Internet. In the case of a TCP read error, the GWIA is reporting that it was expecting to receive data from the other host, but did not receive it. Eventually the GWIA will time out and report the error. A TCP write error is just the opposite of a read error--this means that the GWIA was trying to send data to a remote host but was unable to send the data to the destination within the specified timeout.

Check network connections, cables and switches. Changing the cable and the port for the switch has been known to resolve this issue at times.

The cause of these errors is never the GWIA itself (aside from the corrupt message in the send folder). The GWIA reports these errors because it is trying to communicate with a server on the Internet and is not able to. 100% of the time, the problem is the result of a firewall misconfiguration, a bad router, or other sort of communication problem.

There are a few possible workarounds to this problem, but these are only workarounds to mask the problem---these are NOT solutions.

1. In a few cases, increasing the timeouts in the SMTP/MIME settings | Timeouts button of the GWIA will increase the GWIA's tolerance for slow communications. This is a good first step when troubleshooting these issues.
2. Set "tcp Defend Land Attacks" to ON. This will help clear half-open TCP connections if the connection buffer is filling up.
3. Increase the number of send and receive threads.
4. Verify the PTR record for your site is correct. Some sites will do a reverse lookup on your IP address. If the PTR record is not there or incorrect the site may drop the connection.

If these workarounds do not work, then the resolution to these errors will ALWAYS lie outside the scope of the GWIA. Do not waste time trying to "fix" the GWIA in these cases, since the GWIA is not actually causing the problem, it is merely reporting it. If they do work, it is advisable to find the root cause of the problem, since these 4 steps will not solve the underlying communication issue.

450 Host down

This means that the GWIA was successfully able to resolve the host in DNS, but no response came back when the GWIA tried to contact the receiving host. There are several possible causes of this error:

1. The receiving host was down and/or not accepting mail when the GWIA tried to contact it. The only way to resolve this is to wait for the other host to come back up.

2. A communication problem prevents the GWIA from contacting the receiving host. Sometimes this error is inconsistent and the GWIA will get 450 errors from some hosts and not others. The same issues that can cause 420 TCP read/write errors can also cause 450 host down errors. Again, the communication problem may be anywhere between the two servers involved in the mail delivery.

3. GWIA is loaded with the /mh (relay host) switch pointing to an IP address which is not really a relay host. This will cause a 450 host down error on every outbound message.

4. Port 25 is blocked on the firewall (inbound and/or outbound).

5. If the host that is "down" is the GWIA's own domain name, this is usually caused by the GWIA running on a server with a private IP address which accesses the Internet through NAT. This can be remedied by adding a route.cfg file to the <domain>\wpgate\gwia directory. The route.cfg file is a simple ascii text file which will contain the following:

company.com [Internal IP address of GWIA server] (The square brackets are necessary)

6. Resolv.cfg file is not configured correctly.

7. If using a Cisco PIX router, make sure Proxy ARP is disabled. If proxy ARP is enabled, it will try and answer the ARP requests being done by the GWIA server causing name resolution to fail.

document

Document Title:	400 level GWIA error messages, their causes and resolutions:
Document ID:	10060050
Solution ID:	NOVL38569
Creation Date:	26Jan2001
Modified Date:	28Jan2005
Novell Product Class:	Groupware NetWare Novell eDirectory

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