POP3 collection timeout?

[deftech]

Hello you fantastic New Zealand programmers!

I'm curious to know how long POP3 collection attempts to collect mail before it timesout, and if this setting is user programmable?

I ask because our outside mail server is having problems with high cpu utilization. The utilization is causing exim (our mta software), to respond very slowly. When Wingate goes to check our mail server, pop3 collection will wait there and sometimes hang completely.

I know this is not the fault of Wingate, but our web server acting slow. Until we get our web server back in order, I would love to see Wingate maybe wait a bit longer for it to respond, is this possible with the settings available to me?

If not, thanks anyways. Hopefully these DDOS attacks on our server will end soon so things will go back to normal :))

[adrien]

Hi

You're too kind!

POP3 collection uses the timeout settings of the SMTP server, so you can adjust it there, although it then also affects timeouts for SMTP reception. I should probably make it have its own timeout setting.

Also we recently found a problem with POP3 collection if there is a non-compliance in the POP3 server it is collecting from relating to the UIDL command. Some POP3 servers it seems parse message headers to get the message ID, which they use for the UIDL response. If something stops the parsing of the headers (i.e. incorrectly wrapped header before it), then such POP3 servers can return invalid UIDL responses to some particular messages. The biggest ISP in New Zealand suffers from this problem.

This causes the current version of WinGate to discontinue POP3 collection processing until it times out.

The sure way to check what is going on is to turn on debug logging in the SMTP server, and check the POP3 collection log files.

Adrien

[deftech]

I am still having problems with POP3 collection just hanging. I don't have any antivirus on it. Everything else works fine with Wingate.

I have checkd the pop3 collection logs, and see no errors. It just appears to be checking a user account, and then just stops...nothing..no error.

It seems to happen when our outside mail server hits high utilization. I lowered the timeout setting for pop3, but it doesn't seem to work. Whatever is causing POP3 to hang, it isn't timing out after 60 secs (what I currently have it set to).

I'm desperate to solve this problem. Thanks guys!

[adrien]

can you post a snippet from the logs in this case?

Adrien

[deftech]

This is the end of pop3 collection log. Right now the activity window appears to be hung on many of my users pop3 accounts...but what is wierd is that the log is continuing to get written to, and it appears to be checking pop3 accounts that ARENT' listed as being hung.....does that make sense?

[adrien]

Hi

That log looks mostly normal. It shows a bunch of accounts that have no mail, and one that has 3 messages that get downloaded and deleted from the server.

The one odd thing is the lines

+OK 0 0
+OK Bye!

coming back from the server. like it is resending the response to the previous command. however, since this is in response to the QUIT command, and the connection is then being closed (get the Traffic log entry), it indicates it's not causing a problem.

Which of these accounts appear to be hung?

Adrien

[adrien]

Ah

did you mean that this is the end of the file, which only shows activity from sessions that aren't hung?

Can you look through the log file and find the bits relating to the activity on the sessions that are hung?

Adrien

[deftech]

no

[deftech]

woops I already told you the above. Here is a snippet of an account that is hung. at the end of the snippet is my account ricardo@rings-things.com.

That is the last time pop3 collection checked my account, but is continuing to check other accounts.

[deftech]

Would it cause a problem if I had 25 accounts checking pop3 every 5 minutes, and 1 account checking every 1 minute?

I had to restart the engine a bunch today...:(

[adrien]

Hi

It's weird that the pop3 server reports that 0 messages take 558 bytes

"You have 0 messages totaling 558 octets"

It clearly indicates from the response to the STAT command that the mailbox is empty, and then WinGate sends QUIT, and the session terminates. It does terminate correct? If need to make sure, turn on logging of session termination.

Adrien

[deftech]

Ugh, I think I am running around in circles, and may be wasting your time.

Our main mail server is getting denial of serviced so hard every day. We are starting to see that wingate works fine as long as our mail server is not under a heavy load.

So the only problem we may be seeing with wingate is that it isn't timing out or refreshing the activity screen. Is there a way to make wingate pop3 to just stop or time out or quit if it can't collect pop3 mail, so we don't have to stop/start the engine when we are having a problem? Like a 'reset pop3 collection' button.

I appreciate your respones Adrien..:) Sorry about all this. This DDOS attack is getting very tiresome, and we are under attack constantly. Just we think we are ok, we get hit hard again.

[adrien]

Hi

What are they trying to DOS? If it's a TCP service on that machine, can't you enable SYN protection?

It actually comes in the OS from Win2k onwards I think.

Adrien

[adrien]

PS, POP3 collection uses the same timeouts that SMTP reception does - specified in the timeout setting of the SMTP server.

Are these timeouts enabled?

Adrien

[deftech]

Our mail server at our ISP is what's getting ddos'd. EXIM to be specific. Our wingate machine is fine, it downloads mail from our webserver at our ISP.

We finally ended up changing our MX record to point to a barracuda spam/firewall appliance to filter the smtp connections, so our mail server doesn't get bogged down. It's working great so far. Wingate is doing well also.

SOrry for wasting your time on this :(

[adrien]

No worries, we're always interested in tracking down problems.

Adrien

[deftech]

Well, we solved the denial of service on exim, so our mail server at our ISP is running at a normal load, and Wingate pop3 collection hasn't hung once!

It has been 4 days and no problems! I hate spammers!!!!!!!!!