anuragbhatia.com !!!

This is a question that I have been asked many times via email and sometimes even phone!

Situation is this: you wake up in the morning and found your email hosting is down. You are not getting any emails, either they are bouncing back or going to a blackhole.

What should you do in such a situation?

Email service is much like a chain – if any part is broken, you won’t get things working (apart from lots of frustration!). Since it’s like chain, one must follow step by step to find the problem.

So at this point a good question can be – where does the chain start?

Email hosting consists of 3 parts:

1. Domain Registry record
2. DNS Hosting
3. Email Hosting

Domain Registry record:

Start by checking the domain registration. You can do that using any whois service like who.is, drwhois.com etc. Make sure your domain isn’t expired. If it is, quickly visit your domain registrar control panel and renew it. Most smtp servers keep re-trying to deliver email for around 48hours, so if your domain is expired, you should renew it quickly so that future attempts at delivery will work correctly.

DNS Hosting:

If domain registry is OK, then proceed with checking things at DNS hosting.

DNS servers play an important role in email delivery by giving your MX record to sender’s server which is like an “address” of email host. So you can try sending a DNS query to dns servers for MX records.

You can use online nslookup tools like Zoneedit’s nslookup or network tools nslookup or if you want to try to lookup from your system, use “nslookup” command in Windows DOS (as shown here) and “dig” in Linux (shown here). If server doesn’t returns MX records, then try looking up for “SOA” on that server for your domain. You will probably find no SOA records which “technically” means that server isn’t hosting dns records for your domain. In real world it can be billing issues with host or accidential removal of domain. If you don’t see any SOA records, immediately contact web host via phone. If you are using any decent web host, you can expect things to be up within a couple of minutes. Otherwise I would recommend using any free dns host like editdns or zoneedit. Just signup for a free account with them, add your domain, and then DNS records (MX and A records) followed by change in name servers of your domain.

Email Hosting:

If your DNS server is returning MX records, you can proceed to the next part of chain – email hosting. If your MX records are OK and you are still not getting emails, your of email is likely bouncing and the bounced email will include the “cause” of the bounce back. It can be email account doesn’t exist or server is not accepting email. In most such cases, you would have to contact your email host for help and it can take a day or so to sort out the issue. The best thing you can do in such time is set up a temporary redirection – based email host to prevent bounce back.

You can use free email forwarders like zonedit or editdns to get all incoming emails forwarded to your personal gmail/yahoo account.

To setup forwarding – signup for a free account with provider, add your domain and setup email forwarding for all incoming emails.Then query the dns server of that host for MX records of your domain and set those MX records at existing dns hosting (to prevent hassle of shifting dns hosting).

Summary:

Happy hosting!

Everyday we hear terms like VoIP, IP telephony, voice chat, etc. Ever wonder “exactly” what these mean? Here’s a brief overview of what “IP telephony” is and how it really works?

To understand IP telephony, we first need to understand “VoIP”. VoIP stands for Voice over Internet Protocol, which means carrying “voice” over the “Internet”. VoIP is a broad term which has a number of applications.

Now a good question can be – what’s the advantage of carrying voice over Internet?

The simplest answer is – it gives extremely cost efficient communication. You might be wondering why it’s cheap compared to telephone service? The answer lies in the fundamentals of communications. Let us understand what the technical difference is between a telephone call and a voice chat (i.e., carrying voice over telephone line vs carrying voice over Internet.)

Conventional telephone lines are based on technology called “circuit switching”, while most Internet connectivity technologies are based on “packet switching”. With circuit switching, a circuit is “leased” or “locked” during communication and billing is based on the time period of “leasing circuit”. With packet switching, data is broken into small packets and sent to the other party over the Internet. These packets can choose any available route.

You can visualize circuit switching as:

Here A has to communicate with I. When A initializes a call, it will “lease” a line via B – C – D – E – F – G – H to I. This “lock” will remain there unless A disconnects. In this way, there is a dedicated line between A and I for the duration of the call. Since A and I won’t be transferring data constantly, this approach wastes lots of resources.

To resolve this problem, most modern connectivity technologies use Packet switching. You can visualize it as:

As we can see, in packet switching – “packets” can follow multiple paths based on availability of path. Now to send data from A to I, obviously shortest way is to send data directly as they have a connection, but if that connection is busy, it can follow route via B or C and so on. In all the cases, circuits (“lines”) will be leased ONLY for the time required to transfer the packet and thus billing is done on the basis of “number of packets” transferred.

Breaking data into packets gives a lot of flexibility and makes transfer very cheap but circuits are “shared” one can’t guarantee for availability .

This is why a voice chat is cheaper than a phone call.

Next comes IP telephony. It simply means “telephony”  over IP (i.e Internet Protocol). IP telephony is an application of VoIP. IP telephony works by carrying telephone calls.

Can we connect to any phone in the world from Internet for free?

Answer – No!

Let’s understand how IP telephony routes phone calls. We can understand it by comparing it with a conventional phone call.

I want to call my friend Micheal in New York . So I have two options – either a phone call or IP telephony call from a service like skype. If I make an ISD  phone call, the whole path will be covered by a “dedicated” line between me and Micheal. This will give us a high quality but expensive voice call. But if I call via skype, my voice will be converted into data packets and will be transferred via skype’s network, to the point much closer to Micheal, such as a sub-exchange in New York. The call will then be routed to a phone network (PSTN). Thus a route from India to New York will be covered by packet switching. This enables IP telephony providers like skype to provide cheap International calling as most of calls are carried over the Internet to the closest point and then terminated to PSTN. Since the call has to enter telephone network at the end point (i.e last mile), IP telephony costs are similar to local calls. If both parties are on Internet, we don’t need to enter telephone network at all and, therefore, free voice calls are possible in the “same network”.

Advantages of IP telephony over conventional phone:

• Low cost
• Based on packet switching and hence more calls possible over existing network
• Not based on location, only depends on the location of person you are “calling to”
• Good for mobility, you just need an Internet connection

It sounds like IP telephony is a hero in the communications world. Is it?

No!

IP telephony depends a LOT on the quality of your Internet connection. Quality doesn’t simply mean the raw download speeds, but also factors like QoS, jitter values, overall latency, codecs used, etc. These factors make IP telephony suitable ONLY for very good quality Internet connections. Apart from that, many countries (including India) do not yet allow IP telephony. Therefore, your IP telephony calls are routed to these countries over conventional leased circuits – making it an expensive deal. We can’t really compare the ease of using a “telephone” with a headphone-based skype call. IP telephones are improving, but the technology is new and overall quality suffers.

Why do providers like skype claim better quality calls compared to landline phone?

Logically speaking – they are wrong, and in real world, they are mostly wrong! A VoIP call still isn’t as good as a leased circuit-based phone call. Providers like skype can claim better quality because they call it “digital sound”. PSTN is an analog technology (i.e., the link between the PSTN switch and your home phone is analog) and can get  noises, etc. which isn’t the case with VoIP calls. But to be honest, VoIP itself has so many quality issues, that we can’t really say that it provides the best quality.

So where does the future lie?

The future lies in IP telephony. No doubt!
The biggest problem with IP telephony, as stated, is quality of Internet itself. As we are advancing, more and better networks are being developed with low latency and guaranteed QoS. Also, the “softphones” are being replaced with cheap IP phones, making VoIP independent of computer.

I hope this explains IP telephony.

Thanks for reading!

Hello all!

Few days back I visited Official Google Apps forum (one of my favorite places ) and answered many questions. It was quite after some time i was there and found few cases/questions/problems as really interesting.

Here’s one of the questions asked there by a admin named aol985 about SPF records.

His question -

As described in http://www.google.com/support/a/bin/answer.py?hl=en&answer=33786 , I set SPF record for mashfilm.ru domain to “v=spf1 include:aspmx.googlemail.com ~all”. But aspmx.googlemail.com currently does not resolves. Is it correct?

Nice one!

He is right on fact that aspmx.googlemail.com does NOT resolve. Ok why?

anurag@root]$ dig aspmx.googlemail.com a

; <<>> DiG 9.3.4-P1.1 <<>> aspmx.googlemail.com a
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42050
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;aspmx.googlemail.com.          IN      A

;; Query time: 100 msec
;; SERVER: 66.33.216.208#53(66.33.216.208)
;; WHEN: Wed Aug  5 02:48:00 2009
;; MSG SIZE  rcvd: 38

[anurag@root]$

Thus no A record which means it won’t resolve, BUT one must remember that a zone can have many records working side by side offering their own feature, like – MX records can be there with/without A, same with txt records, and few other also.

Now observing the spf record by Google – “v=spf1 include:aspmx.googlemail.com ~all”

here include:aspmx.googlemail.com

means to include the spf record of aspmx.googlemail.com which makes sense as:

[anurag@root]$ dig aspmx.googlemail.com txt

; <<>> DiG 9.3.4-P1.1 <<>> aspmx.googlemail.com txt
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 30134
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;aspmx.googlemail.com.          IN      TXT

;; ANSWER SECTION:
aspmx.googlemail.com.   7178    IN      TXT     "v=spf1 redirect=_spf.google.com"

;; Query time: 14 msec
;; SERVER: 66.33.216.208#53(66.33.216.208)
;; WHEN: Wed Aug  5 02:54:02 2009
;; MSG SIZE  rcvd: 82

[anurag@root]$

Now it means spf record for aspmx.googlemail.com is “v=spf1 redirect=_spf.google.com”

Now trying to understand _spf.google.com

underscore right in start makes it different from a sub-zone since it can’t be used as a domain but will still remain a working sub zone in terms of DNS.

So now since it can’t be used as a  sub domain i.e which can be used to be attached with web server and can supply pages via ftp, there is no meaning of A record for it here.

Checking txt string of _spf.google.com

[anurag@root]$ dig _spf.google.com txt

; <<>> DiG 9.3.4-P1.1 <<>> _spf.google.com txt
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52983
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;_spf.google.com.               IN      TXT

;; ANSWER SECTION:
_spf.google.com.        300     IN      TXT     "v=spf1 ip4:216.239.32.0/19 ip4:64.233.160.0/19 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:209.85.128.0/17 ip4:66.102.0.0/20 ip4:74.125.0.0/16 ip4:64.18.0.0/20 ip4:207.126.144.0/20 ?all"

;; Query time: 29 msec
;; SERVER: 66.33.216.208#53(66.33.216.208)
;; WHEN: Wed Aug  5 02:57:26 2009
;; MSG SIZE  rcvd: 229

[anurag@root]$

And here we got it!

So much information in just one hostname!

“v=spf1 ip4:216.239.32.0/19 ip4:64.233.160.0/19 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:209.85.128.0/17 ip4:66.102.0.0/20 ip4:74.125.0.0/16 ip4:64.18.0.0/20 ip4:207.126.144.0/20 ?all” is a part of SPF record which Google makes its Google Apps users to use.

Thus using

“v=spf1 include:aspmx.googlemail.com ~all” in spf tells that “this domain allows all of the server on this ip range – ip4:216.239.32.0/19 ip4:64.233.160.0/19 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:209.85.128.0/17 ip4:66.102.0.0/20 ip4:74.125.0.0/16 ip4:64.18.0.0/20 ip4:207.126.144.0/20 as authorized to send email on behalf of that domain.

So that’s how spf works in this case.

(11 votes, average: 4.64 out of 5)

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I found a few great web hosts, which are really cheap yet reliable for Professional Website Hosting. So thought to put a review about them here.

Today will discuss – Bluelemonhost

Its one of the cheapest host i had seen on web, that too with cPanel and 99.9% uptime! 

I had used it personally & its really good.

Good things about it:
 

• Too cheap …basic plan costs $11/yr only.
   
• cPanel based panel….thus really cool to manage things.
   
• Great link speeds….as per my tests – uplink – 3.5MBps and downlink – 2.8MBps (though appears to be little slow…but believe me its far better then expensive Dreamhost!)
   
• Good support….always responses with “done/solved/ok”
   
• Daily free backups with free restoration (nice!)
   
• No irritating limits on number of sub domains, sql databases & users, ftp users and even mailing lists. 

Bad things about it:

• No ssh shell access (but i do accept its useless to give that in plan like $11 an year due to security reasons).
   
• No wget allowed (even via cron jobs) though good way out is just using ftp commands in shell but again that’s not for home users. 
   
• Irritating limit- in $11 plan you can host only 1 addon domain & parked domain.
   
• No great cPanels addons like website builder or templates. (though you won’t need those ever!)

I recommend it using just for personal blogs and small professional sites because of its cost, features it just provides really solid hosting for personal blogs but because of limitations i won’t recommend it for an advanced user.

Cheers!

After recieving lots of emails regarding SRV records issue in Google Apps, i finally tried that in myeslf……unfortunately thats true that Google has missing info. about SRV records.

As per refering to official Google’s help here .

It has missing info. about the location servers.

Here are those missing SRV records…

_xmpp-client._tcp.YOURDOMAIN.TLD. IN SRV 5 0 5222 talk.l.google.com.

_xmpp-client._tcp.YOURDOMAIN.TLD. IN SRV 20 0 5222 talk1.l.google.com.

_xmpp-client._tcp.YOURDOMAIN.TLD. IN SRV 20 0 5222 talk2.l.google.com.

_xmpp-client._tcp.YOURDOMAIN.TLD. IN SRV 20 0 5222 talk3.l.google.com.

_xmpp-client._tcp.YOURDOMAIN.TLD. IN SRV 20 0 5222 talk4.l.google.com.

so finally saying…..just forget everything and have these SRV records to get your domain’s Gtalk working from external IM services…

I created a public G.docs spreadsheet here for easy viewing.

Feel free to post for any issues…

FAQ ON GApps SRV Records

[faq list Google Apps SRV Records]

[faq ask Google Apps SRV Records]

Hope this will help you out

(16 votes, average: 4.44 out of 5)

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