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Old 05-05-2004, 08:09 PM   #1
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Registered: Mar 2004
Distribution: Slackware 11
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Post Can't get to IMAP server through iptables firewall/router

I have a computer that I've been running as a dual boot WinXP/RH 9 box for a while without any major problems. Up until recently, this computer was connected directly to the cable modem, and iptables was used as the firewall. Now I have my girlfriend's old computer pulling router/firewall duty, also with RH 9. I'm again using iptables as the firewall on the router. The network is great, I can ping every computer in the house, and I can get on the internet through the router.

The problem is that I can't check my e-mail on an IMAP server anymore. This goes for both the Evolution and Outlook clients. I haven't changed any of the configs for either of these. Also, since the old computer is acting as firewall, I have all the iptables rules set to "ACCEPT" on the "main" computer, so there's that much less of a chance of packet loss on the LAN. I know this isn't the most secure setup in the universe, but I'm trying to get the d*** thing working. One step at a time.

On a hunch, I took out the router recently and connected the "main" computer straight to the cable modem again. As soon as I did this, I could download all my messages (about 40 by then ). When I put the firewall/router back in the loop, I got the same problem that I had been having before. Outlook says something about the connection timing out or being on too long, and Evolution says that it's scanning the IMAP folders, and it shows the folders that exist on the server, but it never downloads any messages. After about half a minute, it just stops, as if it did everything right.

I ran ethereal on both the public NIC on the router and on the (only NIC on the) main computer while trying to check my messages, with a filter to only capture the packets going to and from the IMAP server. The number of packets captured on each computer was identical (which I considered to be a good thing), the corresponding packets on each capture seemed to match each other, and for each transmission from my computer, there seemed to be a response from the IMAP server. BTW, this is a secure IMAP, so it runs on port 993.

Long story short, I don't know what's happening to prevent me from accessing this IMAP server. Like I said, none of the config settings on Evolution were changed, and it worked consistently before. Also, every single other program that uses the internet works perfectly, just not Evolution. (The inbox monitor never works right either, but, well...)

Anyone have any ideas?



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