Nice to know this exploit to drain the other party's credits..

It doesn't.

The practice of sending someone a message and having it charge them would be illegal as you cant be charged for the actions of someone else where you don't have a choice (not in the uk anyway) this is why we cant be charged for incoming calls, why a person roaming abroad had to pay the international part of the call and why you always have to text FIRST to 80708 to get a kak ringtone. If someone texts you and it costs you 10p and you had no choice in that matter then it would be unlawful.

Some networks used to charge YOU for a delivery reports but the handling of message delivery is handled by the SMSC. When the sms is delivered to the phone it sends an acknowledge back as part of the communication. The centre then relays if its been delivered (the report message is not sent by the phone). This is why text messages don't really cost the operator anything as its all part of the GSM system. I still remember when Text messages used to be free. Back then you could only send so many a day and it was only when the networks saw a nice money earner that the charging factor came into play. I remember my brother getting a shiny letter from Orange saying "Hey guess what. We have removed the sending restrictions on Text Messages. Each message will cost 5p...." or words to that affect

Text messages actually use the same system as every other GSM message. Their is a Data Header which contains the message type (voicemail notification, sim update, flash message etc) and their is scope for thousands of different "types". In reality only a few dozen are reserved GSM types but some phone providers look for custom ones so they can do things like send settings, logos, ringtones etc over the air (or they did back in the day) Some of us old bastards will remeber downloading programs for our pcs that let you send out nice messages to your friends that turned their voice-mail indicators on (very annoying/amusing)

As well as a header they also have a payload. In the case of a SMS the payload is a 160 character ASCII message as well as supporting data such as reciever, message center number, messageid etc.

Wether you get a delivery report or not is simply one bit in the header that's either 1 for yes or zero for no. 02 simply looks at the header of all messages and sets the delivery flag to zero regardless. This change was actually made back when they were BT Cellnet and it was apparantly because their network was struggling under the load of all the text messages and then subsequent delivery reports (most phones have delivery reports turned on by default). Before this delivery reports worked on their network (I remember owning a BT cell-net phone and getting rid of it not long after for at the time pastures new )

Whether you believe their reason or not is up to you. Either way their SMS centre looks for a string at the start of the message and if its present it generates a delivery TEXT (not report) and sends it to the asker. This forces people to ASK for delivery confirmation rather than just having their phones do it anyway for lolz or cba to turn it off.

Their were plans of charging people 2p for delivery reports around the time they did it and I think they feared the customer backlash when everyone with it turned on suddenly got raped 20% for text messaging costs (this was before free messages became mainstream either way I never found out as I went to Orange not long after.

Fully agree
I feel bad for the US folks, many (usually prepaid) get charged for receiving calls.

Someone should do something about it

I'm on O2, delivery reports only worked for MMS for me, I used to get a little 'delivered' message on my N82 and an entry in the 'log'.

However, as MMS messages are now handled via fMMS on the N900 it might be worth having a word with Nick Leppänen Larsson to get this enabled, and then if you require a delivery report you could send your SMS via MMS if you get my drift.

It's an accepted part of US phone life. Americans want cheap calls. To turn round to an average joe and say "yeah, it's gonna cost the same to call a cell in the next room as it is to call England" wouldnt have washed, so they make the person carrying the phone bear some of the cost of the call, (just like when an english person goes roaming)

Americans were so used to cheap calls, that calling a cell wouldnt have taken off in popularity if the caller had to bear the whole cost of the call.

The logic is sound: if youre so big and important that you have to carry a cellphone so that anyone can call you, any time, then why shouldnt you pay for part of the call?

I don't feel that bad for them; some networks have a plan where you jsut pay $x per month and that's it; unlimited everything.. I feel bad for the idiot friends I have who buy the cheapo £20 a month plan "because they don't want to spend a lot on their phone each month but they want to have a new, shiny thing" that gets 150 texts, and then they send 2000 texts a month and get a £185 bill. £20 a month off o2 would have got them 700 minutes and unlimited messages, but they would have to use a second hand phone off ebay..

Ah, how vanity costs..

Anyway, it's digressing.. back to slightly on topic:

the *0# prefix for O2 has a corollorary on Orange: start the message with RCT, though orange does support delivery reports..

Though an MMS knocks 4 texts off your balance rather than just 1, on O2 (even when roaming, just like 1 roaming SMS costs 4 off your allowance; bonus!) so be careful.. *0# is the better bet

Your lucky o2 still do that. MMS are still heavily ripped off on most networks and (for contract anyway) most wont do plans with inclusive mms.

The delivery reports for MMS and exactly the same as SMS although I imagine some sort of messageid is used somewhere.

t-mobile have delivery reports, i dont use it.

OFF TOPIC DIVERSION>>>

There used to be lots of codes like that, which you could use to, for example, delay the sending of your text a certain number of minutes, etc. I used to have a list of them, but lost it. Can't find the site that I found the original list on. No-one seems to be able to tell me where to find the codes.
Anyone know where I could find them, please?

I had this problem on my network... I know that notifications work, prefix is just "!" but when I did that, nothing happened... Then I went abroad and when I was in roaming, delivery worked like a charm... What I did is that I took another Sim card from same operator (I came in my home network) and it was newer that this not working... I surprised when I found out that everything was working perfect. I started a Bugzilla for this and in meantime discovered "solution"
Cheers