SUMMARY
Using POP authentication to authorize relay through a server can be inhibited by the environmental issues.
DETAIL
How does POP before SMTP work in
MailEnable?
Dial-up and large ISP port
blocking
Using dial up and some ISPs
can prevent the usage of POP before SMTP authentication, as the port 25 has been blocked
for all SMTP traffic except through the ISPs service.
Dial up IP change can affect POP before SMTP
relay.
Another problem that can
occur with dial up is due to connecting IPs changing for each connection. With a dial up connection, a
connection is made through POP and mail retrieved, or authentication credentials passed
and the PBS file is created and named after the connecting IP address. The problem occurs
when the next connection is made for SMTP sending or relay. With dial up, it is
very likely that a new connection will have a new IP on the client side which
will be rejected for relay, as the IP verification is not matched due to a different IP
address being used.
Proxy or
firewall
If the problem is occuring with clients across multiple
domains, then there is a chance that a proxy or firewall is blocking the port or
redirecting the traffic. This can especially be an issue with Cisco
routers as they intercept all SMTP requests using a feature called MailGuard.
This service will disallow authentication even if the client and server
sides are configured correctly for relay or authentication. For
information on a solution to this issue please check the following link:
http://www.mailenable.com/kb/content/article.asp?ID=ME020159
Antivirus
firewalls
Some antivirus firewalls can stop the authentication. To
verify this is the issue, disable the antivirus
firewall before authenticating to see if the problem is still occuring.
If the antivirus firewall is causing the issue, then either remove/disable the
firewall compenent of the software or configure the firewall to allow the desired
traffic.
Extra client
diagnostic logging feature
A useful tool for
diagnosing client - server communication from the client side is the Outlook Express Maintenance
feature.
To enable Outlook Express Maintenance;
1. Open
Outlook Express
2. Open Tools
3. Click on Maintenance Tab
4. At the bottom of this tab is a troubleshooting
section. When a mail protocol is enabled in this view, all client access using
this client will be logged into
a [protocol eg.IMAP.log] file.
5. The location of the log files can be found by clicking on
the Store Folder button above the troubleshooting section.
Here
is an example - C:\Documents and
Settings\User\LocalSettings\Application
Data\Identities\{01E6F266-E532-4153-80BB-2B830831ADC2}\Microsoft\OutlookExpress
Here
is an example of a log output file of a client communication
session;
Outlook Express 6.00.2800.1437
SMTP Log started at 08/25/2004
15:15:29
SMTP: 15:15:30 [rx] 220 example.com ESMTP MailEnable Service,
Version:
0-1.2- ready at 08/25/04 07:11:30
SMTP: 15:15:30 [tx] EHLO
mesrv3
SMTP: 15:15:30 [rx] 250-example.com [218.xxx.xx.xxx], this server
offers
2 extensions
SMTP: 15:15:30 [rx] 250-SIZE 10000000
SMTP:
15:15:30 [rx] 250 HELP
SMTP:
15:15:30 [tx] MAIL FROM: <test@example.com>
SMTP: 15:15:30 [rx] 250 Requested mail action okay,
completed
SMTP: 15:15:30 [tx] RCPT TO: <test@hotmail.com>
SMTP: 15:15:31 [rx] 250 Requested mail action okay,
completed
SMTP: 15:15:31 [tx] DATA
SMTP: 15:15:31 [rx] 354 Start mail
input; end with
SMTP: 15:15:31 [tx] .
SMTP: 15:15:32 [rx]
250 Requested mail action okay, completed
SMTP: 15:15:32 [tx] QUIT
SMTP:
15:15:32 [rx] 221 Service closing transmission channel
Outlook
first time send fail
Outlook attempts to send email before using POP to check for email.
Therefore if a message is being sent and the user has not authenticated via POP
it will fail to send the message. Having the client attempt to send the message
the second time will succeed because the POP authentication would have been
performed.
MORE INFORMATION
Error '503 This mail server requires authentication': http://www.mailenable.com/kb/content/article.asp?ID=ME020135
Product: | MailEnable (All Versions) |
Article: | ME020327 |
Module: | SMTP |
Keywords: | PBS,SMTP,POP,,503,relay,before,trouble,troubleshooting,authentication,error |
Class: | TRB: Troubleshooting (Configuration or Environment) |
Revised: | Wednesday, May 4, 2016 |
Author: | MailEnable |
Publisher: | MailEnable |