Re: [Lilux-help] e-mail problems using Coditel-cable ISP

Hi, I can confirm, for the last few days Coditel has been blocking outgoing connection to port 25 to ANY machine !!! Since this morning they are at least allowing connections to their official smtp relay (smtp.coditel.net) ...... Well done guys !!! It looks like they are trying to force their users to use only their mail server for outgoing mail .... :-( a+ Patrick. On Thu, 2004-05-27 at 16:50, Eric Dondelinger wrote: > Hi Serge, > > > For the past 4 weeks there have been increasing problems, first my > > mails seemed to be rejected by Sendar for some obscure "IP forwarding" > > question and Thierry helped me with that. I had to fix my parameters > > in Ximian Evolution and Kmail (I'm using both, yes, different e-mail > > adresses, different "identities", different repositories etc...) > > ?? Sounds strange. -v please (maybe at the meeting tonight) > > > The last time I was able to send myil from my normal account was on > > Sunday night, since then all I get is some error message saying "unable > > to connect to sendar port 25". > > Try this: > (as root), run tcpdump > (as anyone), telnet sendar.prophecy.lu 25 > Check the tcpdump - you'll see the outgoing packets from your machine > to sendar, you should also see the replies coming. If nothing comes > back (not even ACKs), chances are your traffic is being dropped on > the way - question is where. > > Oh yes, if the telnet works, you'll see this: > bash-2.05b$ telnet sendar.prophecy.lu 25 > Trying 213.166.63.242... > Connected to sendar.prophecy.lu. > Escape character is '^]'. > 220-sendar.prophecy.lu ESMTP Sendmail 8.12.10 ready at Thu, 27 May 2004 > 16:50:02 +0200 > 220 No Spam please! > > (close via "quit") > > > Also try this (as root): > nmap -p 25 sendar.prophecy.lu > You should get: > root # nmap -p 25 sendar.prophecy.lu > > Starting nmap 3.50 ( http://www.insecure.org/nmap/ ) at 2004-05-27 16:32 > CEST Interesting ports on sendar.prophecy.lu (213.166.63.242): > PORT STATE SERVICE > 25/tcp open smtp > > If it says filtered instead of open, again, we'll know packets are > being dropped on the way. If it says closed, the packets are not > dropped but rejected. > > > I _am_ able to retrieve my mails from Sendar though and I do receive > > e-mails on each of my e-mail adresses. > > Different port... > > > I called Thierry and we checked a few things and it doesn't seem to > > come from Sendar, so I called the Coditel (un)help-line to inquire. As > > usual they at first considered I might have problems with Outlook or > > perhaps a trojan on my system, I explained that neither Kmail, nor > > Evolution, nor Linux are all that suscpetible to windows virii (they > > were actually understanding about that) and said there have been > > "several" reports of users having trouble sending e-mail, they were > > surprised though that I _am_ able to send e-mail with my Coditel > > account (surprise, this works) > > ... which I assume you're sending via the Coditel mailserver? > > Note: whatever mail you're sending out, you're _always_ supposed > to go through your ISP's mailserver. If you're trying to deliver > mail directly, chances are that the recipient's mailserver will > see your IP as belonging to a DUL (dial-up list), and thus refuse > to talk to you (as much spam comes from dialups, be that analog, > ISDN, dsl or cable). > A From: (or envelope Mail From:) is easily forged, so if the > server allows you to send mail based on that only, it's to be > considered an open relay. If it uses pop-before-smtp or smtp-auth, > things look better. > > Now, when trying the above - get Thierry to have a tcpdump > running on his firewall (I bet there must be one ;-)) to see > whether the packet arrives there. Give him your IP address > first, so he can filter directly for your traffic. A short > phone call will make sure it's no problem on TC's end. > > > 3) Sendar responds to ping, but I can't ssh to Sendar either, might be > > similar filtering from Coditel, how can I investigate this? > > IMHO that would fit the bill. > > > 4) any other suggestions > > Ask Coditel whether they are filtering traffic. Ask them whether > they block outbound SMTP traffic (unless going through their > mailserver - this makes a lot of sense, considering all the mail > resp. Outlook viruses as well as spam), ask them whether they > filter anything else, whether they force your HTTP traffic > through a proxy etc. > > I can very much symphathize with them if they are filtering > outbound SMTP traffic (I'm seriously considering this measure > @work), I can understand if they use a web proxy, I very much > understand if they drop ports 137-139 traffic (SMB), but they > certainly should bloody leave alone an SSH port (22). > > Note, I can symphatize/understand this, but if they do it, they > should inform their customers, and offer their clued customers (tm) > [not that there are many] a way around this. Personally, I wouldn't > accept such a castrated internet connection (and lord, do I sometimes > hate the one at work, where I'm in charge of the filtering myself ;-)). > > Greetings, Eric > > _______________________________________________ > Lilux-help mailing list > Lilux-help(a)lilux.lu > http://lilux.lu/mailman/listinfo/lilux-help