SBS 2008 pop 3 connector won't download emails

Question

We use pop accounts as a backup when our server or internet connection is down. We've recently upgraded to sbs 2008.

I've added our backup pop accounts via the SBS console pop conenctor. When i hit retreive now it give me an error.

in the event log the error is described as:

The TCP/IP connection with the '[pop sever]' server was terminated while 
trying to   access the '[[email protected]]' mailbox. The cause may be 
server problems, network problems, a long period of inactivity, a
connection time limit, or incorrect connection settings.

This only happens if there is a message in the account. if the account is empty it gives no error and says completed successfully. The message can be any size and it still throws this error. It times out in under a minute.

Looking at the pop verbose logs it gets as far as the downloading message stage before it times out. ie it authenticates, checks how many messages there are and begins the download.

I know it's not a firewall issue because i the relevant ports are open on the hardware filewall and the server.

I can download the mail from these pop accounts when i set one up in outlook directly.

I also don't think it's a virus scanning problem as I have this problem even if i disable Symantec Endpoint Protection 11 on the server- which is what we use.

any ideas anyone?

Solution 1

Download the network monitor from http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=983b941d-06cb-4658-b7f6-3088333d062f and use it to watch the connection to the POP3 server.

POP3 is a simple protocol and POP3 commands are plain text. In the output from the network monitor you'll be able to see the commands sent by your server and the responses from the POP3 server. It should be easy to see exactly what the problem is.

The latest version of the network monitor is a bugger to use, but the help is reasonably good and has examples.

JR

----8<---- Response to Charlie's comment:

I doubt the segment lost is significant. TCP is a fault tolerant protocol and even if packets were lost TCP will correct the loss.

If the trace actually shows the mail then the POP3 connector is getting as far as downloading the message. The packet before the mail should be a packet from your server to the POP3 server with the RETR command in it. The POP3 server responds to RETR by sending the mail. After the packet with the mail in, your server should send a DELE command, then finally a QUIT.

If there are no packets after the mail is sent to your server, that suggests your server is failing to spot the end of the message so it's hung waiting. This rings a faint bell with SBS 2003. I have only a faint recollection of this, but I'm fairly sure I've seen something similar in 2003 and that was due to the anti-virus. Someone had installed an AV that processed mail downloads and that was interfering with the connector.

Have you considered uninstalling the AV from the server to see if that helps? We've only done a couple of SBS 2008 installs, and only one of those uses the POP3 connector, but it does work. As a last resort I have actually written a POP3 downloader that I'd be happy to pop on Sourceforge.

Solution 2

You need to do this in the exchange console:

set-connector "pop3 connector name" -ConnectionTimeout hours:minutes:seconds set-connector "pop3 connector name" -ConnectionIdleTimeout hours:minutes:seconds

This will increase the amount of time it will take before exchange assumes that the connector has become idle - even if the connector is still busy downloading mails. This is especially necessary if the server has a slow connection to the internet and/or they regularly receive large mails which might cause the connector to timeout.

This fixed my problem. I hope it fixes yours!

Regards,

Andrew

Comments

[Nizan Freedman]

i have tried this with a different pop account supplier and it does the same thing.

[Nizan Freedman]

Great tool but i'm not sure what it's telling me. I've tried it filtering only pop traffic. the sequence is similar to the pop log. the final entry in the pop sequence is actually the email text which i can read. Just before this final entry there is a line that says: Tcp: [Segment Lost]Flags=...AP..., SrcPort=POP 3(110), DstPort=4562, PayloadLen=577, Seq=1821942727 - 1821943304, Ack=1630571050, Win=65535 (scale factor 0x0) = 65535 i'm guessing the segment lost is significant? do you know?

[John Rennie]

See answer below: I tried commenting but the comment got too long.

[Nizan Freedman]

we use Symantec Endpoint Protection 11 on the server which has no pop3 auto protect on server os's. we use a firebox av firewall for pop3 virus scanning but even turning that off makes no difference and in any case it doesn't stop outlook downloading it directly.

[Nizan Freedman]

i get a RETR 1 followed by a +OK 28214 octets (this is the size of the first message). then it stops. in the nework monitor there's nothing more. in the pop3 connector log it shows Timeout !!! EVENT: The TCP/IP connection with the server was terminated while trying to access the mailbox. The cause may be server problems, network problems, a long period of inactivity, a connection time limit, or incorrect connection settings. (AsyncConn[ ]) Connection to closed. (SMTP) [TX] QUIT it isn't a long period though, only about a min. the messages aren't big.

[John Rennie]

A minute is about right for the timeout. After the POP3 server has received the RETR command and sent the message size it should then send the rest of the message without needing anything more from your server. Why it isn't working I don't know. I would try uninstalling Symantec. NB just disabling it isn't necessarily enough. In any case isn't the POP3 connector in SBS2k8 very limited functionality? I'm sure our chaps gave up on it and used a third party collector.

[Nizan Freedman]

removing the av stuff hasn't helped and i've tried a third party pop downloader - pop grabber. it gives the same error but it doens't when i run it on another pc...