This dialog, accessed from the Service Manager dialog, is used to configure the Post Office Protocol (POP3) Service in Mailtraq. Multiple POP3 Service instances may be configured but, unless multi-homed, each must operate on a different TCP/IP port. The POP3 Service enables mail clients to retrieve messages stored in mailboxes in Mailtraq.
This tab, accessed from the POP3 Service, configures the main properties of an instance of the POP3 Service.
Enable at Startup
This service is enabled when Mailtraq starts up if this option is selected. Configured services may also be started by selecting Start Service from the Tools menu in the console.
TCP/IP Port to listen on
The standard port for POP3 is 110. Mailtraq allows TCP/IP ports to be specified by port number or by the standard service protocol acronym. For example "POP3" (without the quotes) may be used instead of "110". For further information on TCP/IP Ports and Multi-homing see here
Limit to...simultaneous connections
Mailtraq refuses simultaneous client connections above the numerical limit set in this edit box. With a default of value of 25, the minimum number of simultaneous connections allowable is 1 and the maximum is 999.
Mailtraq will initiate disconnection from idle clients after the period set in seconds in the edit box. The default is 60 seconds.
Access Control Tab
This tab, accessed from the POP3 Service dialog, controls which clients are permitted to use this instance of the POP3 service.
1 Allow any client to connect
If this option is selected Mailtraq will allow any client to use this service. This option is not recommended unless Mailtraq is operating behind a separately configured firewall or unless access by unauthorised clients is physically impossible (i.e. in a closed network which does not connect, for example, to the Internet).
2 Use the addresses below as a Firewall
If this option is selected Mailtraq uses the range of IP addresses entered directly into the Limit access to... list box to determine which clients are permitted to use the service. Note that the firewall is empty by default therefore no clients will be able to use the service until a suitable IP address range is entered.
3 (2) and Local Area Network
If this option is selected Mailtraq uses the range of IP addresses entered directly into the Limit access to... list box followed by the range of IP addresses entered into the LAN tab of the Server Properties dialog to determine which clients are permitted to use the service.
The Edit button can be used to display the LAN tab if needed.
Folder Access Tab
If a mailbox contains multiple folders (such as those used by IMAP and Webmail) then POP3 collections on those mailboxes would download messages without knowing what folder they are in.
In hybrid email systems where both POP3 and Webmail are in use Users may wish to have this behavior modified.
This control allows the Administrator to control access to the INBOX folder only (default) or to all folders.
Remove Invalid Message-ID fields
This control allows the Administrator to remove Invalid Message-IDs which can cause some email clients to 'lock-up'. Invalid Message-IDs are generally created by malformed spam either accidentally or as a deliberate attempt to disrupt email transfer.
This control locks the mailbox when a POP3 collection is started preventing subsequent POP3 connections to the same mailbox whilst the first connection is in progress. If the first connection is abandoned the lock is released after the idle time out. Introduced in Build 2126.
This tab, accessed from the POP3 Service dialog, configures the POP3 Proxy. The POP3 proxy enables all POP3 clients to collect mail directly from remote POP3 servers through Mailtraq. Thus, inbound POP3 mail can be configured to pass directly to a user machine without being processed or stored by Mailtraq but retaining the advantage that connections to the Internet remain managed by Mailtraq.
Enable the POP3 Proxy Service
Check this option to enable the proxy service.
USERNAME # HOST.DOMAIN.COM
Select the symbol to use, # (ASCII 35) being the default, from the drop list. The appearance of the selected symbol in the POP3 username sent to Mailtraq triggers the POP3 proxy. Choose a symbol which is also acceptable to the POP3 client programmes being used.
Initiate a Dial-up to connect (Modem-users)
If this option is checked Mailtraq connects to the Internet when a client request contains a non-local domain. Click on Dial-up Settings to display the Scheduled Dial-up Settings dialog to specify how Mailtraq should connect to the Internet.
Only allow connections to these remote servers
Check this option to prevent users from connecting to remote POP3 servers other than those specified in the associated edit box.
- POP3 Client Setup
In the POP3 client, change the user name to fred#remote.server where "fred" is the original user name, "#" is the symbol selected to trigger the POP3 Proxy and "remote.server" is the host name of the remote POP3 server. Change the server name, previously the host name of the remote POP3 server, to that of the Mailtraq server. For example, if Mailtraq's Domain Name is example.com and the original POP3 client user name and server are:-
user name fred
the revised settings to use the POP3 Proxy should be:-
user name fred#pop.isp.com
Some POP3 clients present the user name and server details in a single field, in which case the revised field should be:-
Also, ensure that the password in the local POP3 client is correct for the remote POP3 server.
How the POP3 Proxy works
When the POP3 Proxy is triggered by receiving # in a user name, Mailtraq connects to the remote POP3 server specified in the string following the # (pop.isp.com in the above example), if permitted by the Only allow connections... control (initiating a dial-up if necessary) and issues the string preceding the # (fred in the above example) to the remote POP3 server as the username. Meanwhile, Mailtraq has requested and received the appropriate password from the local POP3 client and passes that on to the remote POP3 server when prompted. Once authenticated, Mailtraq connects the local POP3 client to the remote POP3 server and performs subsequent port translations between the two transparently. Note that Mailtraq, honouring its proxy role, does not log details of the subsequent POP3 session. When either the local POP3 client or the remote POP3 server quit the session, Mailtraq drops both local and remote connections automatically.
APOP authentication cannot be proxied, so POP3 clients wishing to use the POP3 proxy must be configured to use normal USER/PASS authentication. However, Mailtraq reuses the USER/PASS provided by the user to authenticate via APOP with the remote POP3 server wherever possible. If APOP authentication with the remote POP3 server fails, Mailtraq caches the failure (until restarted) and falls back to authenticating with USER/PASS. Some POP3 servers disconnect the client immediately following any form of authentication failure. In such a case Mailtraq will retry (not using APOP) shortly, although it will appear briefly that Mailtraq cannot connect to the server.