Ichabod Dynamic Addresses FAQ

Here is the list of frequently asked questions about Ichabod's Dynamic Addresses. There are also several other other faqs.


What are Dynamic Addresses?
Dynamic Addresses are a tool for preventing spam. They are addresses that are aliases for your email address. But you can embed information in them, such as an expiration date.

For example, if you want to email technical support at wemightspam.com, you can create a dynamic address that will expire in 30 days. That way if they add you to their mailing list, it won't matter (after 30 days, at least).

If you want to by a book from wemightsellyourname.com, you can create a Dymamic Address that will be rejected if the sender's domain is not 'wemightsellyourname.com'.

When should I use Dynamic Addresses?
Any time you are giving an address to someone electronically (e.g. a mailing list, an online purchase, etc.), or if you need to put an address on a web page.

They are a bit too long to actually print on a business card, and no one would want to type it in.

How do Dynamic Addresses work?
They encode the extra information in the email address.

A simplified example might be if your email address was tom@demo.listsite.com, and you wanted an address that would expire on 2001/3/31, you could encode it as


The server recognizes the address as being dynamic (from the leading ..), and then can check the date, and reject the address if it has expired. Note that it doesn't accept the message, then bounce it, it immediately rejects it as it arrives, minimizing spammers impact on your system.

That's not the actual format, the format is a bit more complex, but that's the general idea. For implementation details, see com.worldware.DynamicAddress.java

Are Dynamic Addresses a standard?
Dynamic Addresses are fully compatible with current email standards. That is, any mail system should be able to send to a Dynamic Address, without any changes required.

There is no standard for Dynamic Addresses. As far as we know, they are completely original to Ichabod.

There is no need for Dynamic Addresses to be standardized. A mail server must be able to generate and recognizes its own Dynamic Addresses. Other mail servers an clients just use them as if the were normal addresses.

As long as the receiving mail server understands its own Dynamic Addresses, it doesn't matter if other servers use different implementations. In fact, we encourage different implementations. The more different implementations there are, the harder it will be for spammers to keep up.

Can someone fake a Dynamic Address?
It's unlikely any one will try, until they become more widely used, but Ichabod can already cryptographically sign the Dynamic Addresses, so that shouldn't be a problem.

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