[pmmail-list] Connecting to pop server

[Kenneth Porter]

On Fri, 19 Oct 2001 08:40:18 -0400 (EDT), Ronny Hippler wrote:

>	Don't know if this has been brought up here before, I am constantly getting stuck 
>connecting to pop server. I know this was discussed in the newsgroup eons ago and 
>was hoping that the latest beta would fix this. I am on @home and their servers go 
>through phases of unreliability where this happens constantly. A friend runs the windows 
>version and says he never sees this problem. I am running the os/2 version.

I think there was a fix in one of the betas to increase the timeout on
the initial connection. A lot of ISP's (including AT&T-@Home in the
SFBA) do not provide reverse DNS (IP to name mapping) for their
customers, but they may leave the POP servers set to query reverse DNS
for a client before presenting the welcome banner. The server then has
to go through a DNS timeout once before completing the connection. This
only has to happen once in awhile, as the DNS server will then cache
the absence of a reverse record for a period of time, and subsequent
connections will go through quickly because the DNS server will quickly
respond with a negative answer.

By increasing the connection timeout in PMMail, the first connection
will wait long enough for the server's DNS query to time out and for
the server to complete the connection. This timeout should be on the
order of a couple minutes, as I think the default resolver timeout
works out to about 70 seconds with 3 DNS servers.

To see if this is the issue, try to "manually" connect to the POP
server with "telnet popservername 110" and see how long it takes to get
the welcome banner. (Type "quit" to disconnect.) This should be tested
only after you have NOT connected in awhile, so that the negative DNS
cache time lets the DNS cache entry expire.

To determine the negative DNS cache time, get Sam Spade
(http://www.samspade.org/), use the dig command on your IP address, and
observe the last number in the SOA record, which is the negative cache
time in seconds for that IP block.

Ken
mailto:shiva@well.com
http://www.sewingwitch.com/ken/
[If answering a mailing list posting, please don't cc me your reply. I'll take my answer on the list.]



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