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I've noticed Yahoo Mail has unlimited storage. I've also noticed that the maximum file attachment size is about 20meg, which I can forward without having to re-upload it from my computer.

I was thinking if I had like 20 people each with yahoo accounts, and I forwarded this attached file to all 20 accounts, that would mean that instead of the 20 meg file that Yahoo needs to store, it would now need to store 400 megs of data.

If me and my 10 friends kept forwarding this email back and forth to each other, every time one of us hits the Forward button, it would cost Yahoo 400 megs of storage.

And this number only gets larger as more people want to become involved. And this is all via legitimately forwarding emails, we're not talking if this whole process is automated.

I know Yahoo has got plenty of money and plenty of storage space, but surely if enough people did this enough time, it would start affecting their system right?

It sounds too simple, so is there a way Yahoo would counter this problem?

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closed as off topic by ChrisF, Nifle, Diago Jan 19 '11 at 12:48

Questions on Super User are expected to generally relate to computer software or computer hardware, within the scope defined in the faq.

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The solution to this particular situation is known as deduplication, it was meant to optimize the use of space on drives or in ram but can easily circumvent your evil scheme even though it's not designed to counter it :) See here for a quick introduction on deduplication.

Deduplication can be based on files, blocks or bytes which all have advantages and drawbacks. This article on the ZFS implementation of deduplication is interesting.

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I have a feeling forwarded attachments would be heavily optimized / deduplicated already by big providers like yahoo, gmail etc. – JP19 Jan 19 '11 at 11:57
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Exchange for example introduced deduplication (under the name SIS) in version 4.0: vmlover.com/2009/12/exchange-2010-infinite-instance-storage Exchange 2010 on the opposite doesn't support SIS anymore leading to an increase of disk space consumption howexchangeworks.com/2010/01/… , I suppose it's not a great deal for entreprises because most store Exchange servers/data on platforms supporting deduplication (think ESX + NetApp hardware). – Shadok Jan 19 '11 at 13:18
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