There is *no* general solution to your problem; you have no knowledge of the potential recipient's circumstances so you just have to give it your best shot depending on how serious the situation (ie consequences of failure), and what you believe is a reasonable course of action in light of the transaction type. The level of effort to ensure delivery has to be proportional to the consequences of failure.
The key is to give some choices and either pursue all of them or let the user opt-in to the best for their needs.
You should *push* the info out in various channels that might include email, SMS, snail mail and others.
You should also have a simple way that recipients can *pull* the same data (eg from the web, or the phone). At the start of the transaction you should indicate the time by which a confirmation should reach the user and in the event that it does not how they can initiate the pull.
As already suggested using a PIN as the transaction ID works fine as long as the period the transaction is open is not too long. The longer the time the more PIN digits needed !
If the transaction is a financial one and paid for using plastic then the card number used to buy can act as the PIN. Theatre booking offices use this simple mechanism to ensure that tickets collected at the box office get to the person who paid for them.
All transactions are a two-way street and in your own words if the user *must* read the message then they too bear some responsibility.
All channels are fraught (email spammed, phone out of range or dead) but if you cover push email and SMS and pull from a website and phone you can probably demonstrate 'reasonable endeavours'.
IMHO you should *never* require that anything is printed and bits of dead tree produced as 'evidence'. Trivial to forge and I for one am a full time traveller and usually have no access to a printer.
Regards
BTW never undertake 'best endeavours' to deliver as that *will* be understood as requiring you to do it regardless of time, trouble and expense.
Jake
SMTP is well named. Send Mail Then Pray.
There is *no* general solution to your problem; you have no knowledge of the potential recipient's circumstances so you just have to give it your best shot depending on how serious the situation (ie consequences of failure), and what you believe is a reasonable course of action in light of the transaction type. The level of effort to ensure delivery has to be proportional to the consequences of failure.
The key is to give some choices and either pursue all of them or let the user opt-in to the best for their needs.
You should *push* the info out in various channels that might include email, SMS, snail mail and others.
You should also have a simple way that recipients can *pull* the same data (eg from the web, or the phone). At the start of the transaction you should indicate the time by which a confirmation should reach the user and in the event that it does not how they can initiate the pull.
As already suggested using a PIN as the transaction ID works fine as long as the period the transaction is open is not too long. The longer the time the more PIN digits needed !
If the transaction is a financial one and paid for using plastic then the card number used to buy can act as the PIN. Theatre booking offices use this simple mechanism to ensure that tickets collected at the box office get to the person who paid for them.
All transactions are a two-way street and in your own words if the user *must* read the message then they too bear some responsibility.
All channels are fraught (email spammed, phone out of range or dead) but if you cover push email and SMS and pull from a website and phone you can probably demonstrate 'reasonable endeavours'.
IMHO you should *never* require that anything is printed and bits of dead tree produced as 'evidence'. Trivial to forge and I for one am a full time traveller and usually have no access to a printer.
Regards
BTW never undertake 'best endeavours' to deliver as that *will* be understood as requiring you to do it regardless of time, trouble and expense.