[Ilugc] anatomy of a mail server
I have been screwing around with e-mail based product development work the last 5 years and so I have a fairly good grasp of how e-mails flow along the Internet. Now that reminds me long ago in college I answered a paper about how e-mail flows on the net. I got it wrong. I thought that just like packets flow from hop to hop mails are stored at each hop. I started with spam control and now I also have a mail server. Basically an e-mail that is sent from point A to reach point B on the Internet has to pass through multiple routers the same way a web server is reached. But there are lot of differences. The primary concept is that of how DNS plays with it. A DNS record called the MX pointer is key here. For you to receive mail from the outside world a DNS record has to tell them that the domain you are hosting can be reached on such and such IP address. An MX record is not an IP address. It is a mapping between a domain name and another domain name whose A pointer points to the IP address. $ dig zoho.com mx will tell you. Or $ dig +short gmail.com mx Anyway the point is that for a mail server to function properly it should both send and receive mail traffic. A simple mail server is easily configured using any worthy UNIX operating system. It comes with stock sendmail, postfix, qmail, exim or whatever else. The popular solutions like Zarafa, Zimbra, Scalix, Kerio and so on are built on top of Postfix or sendmail or any such. I use postfix. It is far easier to be able to send mail out than to receive them as sending does not involve MX pointers. Only static IP that is not blacklisted is necessary. If you have that you can easily send mail that is received by most servers. In that regard you may check the popular blacklist sites like senderbase.org used by Ironport which hurt my customer a lot these days(I somehow fixed the issue) and blacklistcheck.org or some such thing. If you have a DHCP address like in a normal broadband then dont run a mailserver. You can only when you can authenticate against gmail and wish to use a smarthost to transmit and receive mail. Not much fun in running such a mail server. Now for how spam control works. I guess most of the technically minded clued in guys would have followed something about e-mail servers. Spam control falls into a technology area identified by Gartner and other MBA companies as e-mail security gateway solutions or network security in case you talk UTM as I wrote two days ago. It is about controlling unwanted mail at the gateway/network level. But just like virus scanning this can be done at the user mailbox level as well using simple Outlook rules. But almost in every case spam control is performed at the mail server. We will discuss that later. E-mails are sent and received using port 25 of TCP, port 587 called as submission port is used in certain cases where it is normally authenticated. And port 110 and 143 are used for POP3 and IMAP4 for downloading mails from mail server to mail clients like Outlook also called as MUA. mutt is the MUA I use in UNIX. Dovecot is the best server for this. It handles authentication for POP3 and IMAP and serves mail from mailboxes. There are other secure variants that use SSL and SMTP auth is another topic for mail relay authentication. But for sure authentication is done during mail download to identify the user's mailbox. For mail relaying/sending it is not a must as the authentication is performed by the IP address as it belongs to the accepted network of Postfix. This is where a VPN is very helpful as you can belong to the local network segment from anywhere in the world by using OpenVPN and connecting to the company's mail server. If not you can use the submission port 587 and do SMTP auth to send mail. I have not configured this so far. -Girish -- Gayatri Hitech http://gayatri-hitech.com ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Mail_Server_Issue
Hi, On Mon, May 14, 2012 at 6:05 PM, Marikkannan Rajagopal wrote: > hi all., > in "admin1and1" and > there i set my localbox ISP (Static IPaddress) as "A Record" and the > redirection are working fine. For mail delivery, an 'A' record alone is not sufficient. You need to add an MX record. Once you do that and the DNS gets refreshed, from some box do "dig your.domain.name -t mx" [1] The results of the dig command will have multiple sections. See if the "ANSWER SECTION" has any hostname for the MX record. You should see something like this. my.domain. 86400 IN MX 10 mail.my.domain. If you get that, it just means that your DNS settings are OK and you should be able to receive mails now if your other settings(postfix an dovecot) are correct. If you still don't get emails. Run tshark/tcpdump on the mail server, send a mail from some provider(like gmail/yahoo mail etc.) and see if you see any traffic. Share the results if you have problems analysing them. Thanks [1] You may have to install dns-utils in debian based distros if you do not have the dig command. -- Thank you Balachandran Sivakumar Arise Awake and stop not till the goal is reached. - Swami Vivekananda Mail: benignb...@gmail.com Blog: http://benignbala.wordpress.com/ ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] New Packages in debian
Dear all I am appending news about new packages in debian Raman.P blog:http://ramanchennai.wordpress.com/ The Debian Projecthttp://www.debian.org/ Debian Project Newsdebian-public...@lists.debian.org May 14th, 2012http://www.debian.org/News/weekly/2012/10/ New and noteworthy packages --- 243 packages were added to the unstable Debian archive recently. Among many others [59] are: * debian-handbook — reference book for Debian users and system administrators [60] * environment-modules — modular system for handling environment variables [61] * gnome-boxes — simple GNOME app to access remote or virtual systems [62] * lightsoff — sight puzzle game [63] * maelstrom — arcade-style game resembling Asteroids [64] * mustang-plug — controller for Fender Mustang amplifiers [65] * swell-foop — colored ball puzzle game [66] * swftools — collection of utilities for SWF file manipulation/creation [67] * termsaver — simple text-based terminal screensaver [68] * unburden-home-dir — remove or move cache files automatically from user's home [69] 59 : http://packages.debian.org/unstable/main/newpkg 60 : http://packages.debian.org/unstable/main/debian-handbook 61 : http://packages.debian.org/unstable/main/environment-modules 62 : http://packages.debian.org/unstable/main/gnome-boxes 63 : http://packages.debian.org/unstable/main/lightsoff 64 : http://packages.debian.org/unstable/main/maelstrom 65 : http://packages.debian.org/unstable/main/mustang-plug 66 : http://packages.debian.org/unstable/main/swell-foop 67 : http://packages.debian.org/unstable/main/swftools 68 : http://packages.debian.org/unstable/main/termsaver 69 : http://packages.debian.org/unstable/main/unburden-home-dir ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] State transition diagram
On Thursday 10 May 2012 06:16 PM, Siva Chandran P wrote: > You can also try PlantUML(http://plantuml.sourceforge.net/state.html) > which can convert textual input to state diagrams. This is really interesting. Thanks for sharing :) -- .o. I'm a Free man. I use Free Software. ..o ooo http://www.joesteeve.org/ signature.asc Description: OpenPGP digital signature ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Summer camp
Hello chidambaresan, On Tue, May 15, 2012 at 6:26 AM, chidambaresan ananthan < chidambasak...@gmail.com> wrote: > Dear luggies, > 2 years back,on behalf of ilugc we conduct summer workshop.why cant we > do that same this year too.instead of weekend workshop,5 day camp is > my suggestion.we also focus the passed out peoples and can help them > to show up the open source career.we can cal 3rd year engineering > students who have the open source lab next year also.whats your > suggestion. That sounds like a good idea. I guess the important factor is the manpower needed to conduct this. Also, unlike weekends, people other than students will have to take leave from office. If you are interested in organising this, please go ahead. People who are interested will join you. Btw, which workshop 2 years back are you talking about? -- Vignesh Nandha Kumar http://vigneshnandhakumar.in ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Mail_Server_Issue
Hi Marikkannan, Can I know what is you domain name ? if your example the domain which you have registered is tamil.com and if you have proper MX record in place, verify it with a website like mxtoolbox.com. -- Regards, Balasubramaniam Natarajan www.etutorshop.com/moodle/ ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] State transition diagram
Hi PlantUML look really cool :-) You can also try PlantUML(http://plantuml.sourceforge.net/state.html) > which can convert textual input to state diagrams. > > Thanks & Regards, > Siva Chandran P > -- Regards, Balasubramaniam Natarajan www.etutorshop.com/moodle/ ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Dual Boot - Help
On May 14, 2012 8:21 PM, "Muthukumar S" wrote: > Also, Please guide me how to make the USB bootable with Ubuntu ISO. Unetbootin.sf.net is a nice app for Linux and Windows which makes bootable USB sticks from ISO images. - Raja ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Dual Boot - Help
Hi, Thanks all. Will try the same and confirm. On May 14, 2012 9:10 PM, "Guruprasad" wrote: > > Hi, > > On Mon, May 14, 2012 at 8:20 PM, Muthukumar S wrote: > > Hi Frnds, > > Also, Please guide me how to make the USB bootable with Ubuntu ISO. I am > > having my ISO image of Ubuntu 12.04. > > There is a tool called 'USB Startup disk creator'. Using that and the > iso image, you can create a bootable usb drive from which you can > install ubuntu. > > For more details refer - > https://help.ubuntu.com/community/Installation/FromUSBStick > > Thanks & Regards, > Guruprasad > ___ > ILUGC Mailing List: > http://www.ae.iitm.ac.in/mailman/listinfo/ilugc ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Dual Boot - Help
Hi, On Mon, May 14, 2012 at 8:20 PM, Muthukumar S wrote: > Hi Frnds, > Also, Please guide me how to make the USB bootable with Ubuntu ISO. I am > having my ISO image of Ubuntu 12.04. There is a tool called 'USB Startup disk creator'. Using that and the iso image, you can create a bootable usb drive from which you can install ubuntu. For more details refer - https://help.ubuntu.com/community/Installation/FromUSBStick Thanks & Regards, Guruprasad ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
[Ilugc] Bridging and routing
This tutorial is about the elusive bridging technology so commonly employed in ADSL routers and stuff but not so generally used in TCP/IP networking. I wanted to talk about VLANs but I have no experience with them. Perhaps later. For now let us focus on bridging. What is a bridge? Since I grew up in the Lakshadweep islands the word bridge only meant one thing. No, not the connection across a river as there are no rivers in Lakshadweep. The topmost part of the ship/liner where the captain sits and where they drive the ship. I have also driven ships and boats. ;) Anyway now the meaning of a bridge is not something we come across often in networking; it is supposed to be a layer II device that does switching; no routing. Somewhat like a hub/network switch. Now a computer with sophisticated routing capabilities can jolly well act as a dumb switch. And switches talk a protocol called STP , spanning tree protocol which is nothing but a way to regulate the traffic. In switched mode packet transmission it is very important. Alright, now let us focus on software and our work. Say we have a situation where we have to extend a network segment between wired and wireless world or even physically across. Obviously creating a different subnet/mask for that is problematic. To keep the network less complicated we can resolve to bridging in which a computer acts as a simple physical interconnection of networks such that the topology does not change. A very good example is my house office. In case I wish to have a LAN downstairs with WiFi upstairs I will use bridging. Now bridging is also employed in ADSL MODEM testing. I have a buddy in BSNL who keeps bothering me all the time with some MODEM that is not configured correctly; he with either have the DHCP address wrong or some stupid mistake in the MODEM will trouble him. And I have always found that people with little ability are seldom benefited by help. Anyway he normally keeps the MODEM in bridge mode and runs a dialer from the Windows desktop to connect to the Internet. What is a MODEM? It is a firewall, router, DHCP server, NAT all in one. What is the advantage of bridging? Except that you can run the dialer from a PC instead of the MODEM itself which talks PPPoE there is no big advantage as such. But it is always good to have an option. A MODEM has an ethernet port, a Wifi port and an RJ11 phone jack which connects to the CO. The public IP is available in the phone network. The local ethernet network has a local IP. The MODEM can only route traffic between the two networks. But you can ask the MODEM to only do the physical connectivity to the exchange server and let the Windows desktop do the PPPoE dialing with username and password. In this case,the ethernet or Wifi port does the work of the phone line to talk to the exchange. It is a very interesting concept if you think of it... -Girish -- Gayatri Hitech http://gayatri-hitech.com ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] OpenVPN's greatness
Excellent. Let us all oldies meet then ;) On Mon, May 14, 2012 at 7:53 PM, Jacob G Podipara wrote: >> >> Thanks. Let us wait and see if your interest will sustain for 10 years. >> >> >> -Girish > I lasted four years now, am 42. Still enthusiastic, learnt a few CLI tricks > too. Hope to continue. > Podi > ___ > ILUGC Mailing List: > http://www.ae.iitm.ac.in/mailman/listinfo/ilugc -- Gayatri Hitech http://gayatri-hitech.com ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Dual Boot - Help
On Mon, May 14, 2012 at 8:20 PM, Muthukumar S wrote: > Hi Frnds, > > > I am using Linux and Windows 7 in my desktop (Dual Boot), where i have to > change my Linux OS to Ubuntu 12.04 Latest version. > > But i am not having CD Player to boot and install. Can any one help me how > to install Ubuntu using USB Drive. > > Also, Please guide me how to make the USB bootable with Ubuntu ISO. I am > having my ISO image of Ubuntu 12.04. > http://help.ubuntu.com/ https://help.ubuntu.com/community/LiveCDCustomizationFromScratch Have you seen this? You can change the BIOS boot order to USB-FDD or USB-ZIP or USB-HDD and boot from the USB stick and install. -Girish -- Gayatri Hitech http://gayatri-hitech.com ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
[Ilugc] Dual Boot - Help
Hi Frnds, I am using Linux and Windows 7 in my desktop (Dual Boot), where i have to change my Linux OS to Ubuntu 12.04 Latest version. But i am not having CD Player to boot and install. Can any one help me how to install Ubuntu using USB Drive. Also, Please guide me how to make the USB bootable with Ubuntu ISO. I am having my ISO image of Ubuntu 12.04. -- regards, Muthukumar ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] OpenVPN's greatness
> > Thanks. Let us wait and see if your interest will sustain for 10 years. > > > -Girish I lasted four years now, am 42. Still enthusiastic, learnt a few CLI tricks too. Hope to continue. Podi ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
[Ilugc] 2 seconds Boot time with systemd
Hello everyone, Recently came across this post in phoronix:- http://www.phoronix.com/scan.php?page=news_item&px=MTEwMjc and upon reading it and came across this good review:- http://0pointer.de/blog/projects/why.html -- Regards, Prasanna Venkadesh PuduvaiLUG Mailing List: http://puduvailug.wordpress.com/mailing-list-guidelines/ FOSS Jobs all over India: http://fossjobs.in ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] Mail_Server_Issue
On Mon, May 14, 2012 at 6:05 PM, Marikkannan Rajagopal wrote: > hi all., > > I configured "Mail Server with POSTFIX+DOVECOT+SQUIRRELMAIL" in > CENTOS 5.3 . > It is working fine in local and also i able to send mail to "Outside mail > server like "Gmail" etc". > But I can't receive mail from gmail to my localmailbox.I register my domain > in "admin1and1" and > there i set my localbox ISP (Static IPaddress) as "A Record" and the > redirection are working fine. > But i can't get the mail from outside server.The mails are bouncing and > generate 550 error. Have you set the correct MX records? ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
[Ilugc] mailServer_issue
hi all., I configured "Mail Server with POSTFIX+DOVECOT+SQUIRRELMAIL" in CENTOS 5.3 . It is working fine in local and also i able to send mail to "Outside mail server like "Gmail" etc". But I can't receive mail from gmail to my localmailbox.I register my domain in "admin1and1" and there i set my localbox ISP (Static IPaddress) as "A Record" and the redirection are working fine. But i can't get the mail from outside server.The mails are bouncing and generate 550 error. What are all the things that i want to do the entire system must be working perfect.please suggest me and reply as soon as possible. Thanks in advance. mohan.S ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
[Ilugc] Mail_Server_Issue
hi all., I configured "Mail Server with POSTFIX+DOVECOT+SQUIRRELMAIL" in CENTOS 5.3 . It is working fine in local and also i able to send mail to "Outside mail server like "Gmail" etc". But I can't receive mail from gmail to my localmailbox.I register my domain in "admin1and1" and there i set my localbox ISP (Static IPaddress) as "A Record" and the redirection are working fine. But i can't get the mail from outside server.The mails are bouncing and generate 550 error. What are all the things that i want to do the entire system must be working perfect.please suggest me and reply as soon as possible. Thanks in advance. -- R.Marikkannan Linux System Admin SoftSolution4U ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
Re: [Ilugc] State transition diagram
> You can also try PlantUML(http://plantuml.sourceforge.net/state.html) > which can convert textual input to state diagrams. > > Thanks, all. Currently, using R for this purpose. Planning to check out PlantUML hoping that it would give more control than R. -- All generalizations are false. ___ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
