Internet and e-mail policy and practice
including Notes on Internet E-mail


Click the comments link on any story to see comments or add your own.

Subscribe to this blog

RSS feed

Home :: Email

21 Apr 2010

More on portable email addresses Email

Last month a bill in the Israeli Knesset would have required ISPs to provide portable e-mail addresses, analogous to portable phone numbers that one can take from one phone company to the other. As I noted at the time, e-mail works differently from telephone calls, and portability would be difficult, expensive, and unreliable. So I was wondering, idly, if we really wanted to provide portable e-mail addresses, how hard would it be?

Telephone number portability works by looking up the number in a global shared database before routing each call. The Internet has a global shared database in the DNS, and each time a mail message is sent, the sending system looks up each recipient address in the DNS to see how to route it. But the lookups are just for the domain name, the part after the @ sign, not for the whole address.

If we could adjust the syntax of mail addresses so both the user part and the domain got a DNS lookup, then it would be technically straightforward to port an address from one provider to another. I realized that some mail systems have done this all along. If someone's mail address were we can put the user name into the domain, and make the address, where the something is arbitrary. I've offered this option to my users for years, as a way to do tagged addresses, with the new form of the address equivalent to at delivery time, something that turns out to take one line of code to implement in the mail system I use.

Several ISPs offer user mail addresses in this form. Panix in New York and Demon Internet in London have done so since the early 1990s, and there are probably others I haven't run into. All of them do this to provide multiple addresses for their users, but with some degree (well, a large degree) of adminsitrative effort, they could arrange their DNS so that specific users' mail is delivered to other mail systems.

If you know in advance that you want to keep your mail address when you switch ISPs, you can register your own domain for $10 - $15/yr, but for people who aren't that adventurous, mail addresses with the user name after the @ sign offer, in principle, portable addresses too.

posted at: 00:43 :: permanent link to this entry :: 3 comments
posted at: 00:43 :: permanent link to this entry :: 3 comments

comments...        (Jump to the end to add your own comment)

I like this innovative suggestion, but would the @ sign even be necessary if this scheme was adopted across the board? If was unique, perhaps we could move away from a universal, redundant, and unnecessary character.

(by Brian S. Pauls 28 Apr 2010 13:49)

The @ sign isn't going away
Your suggestion would require changing every piece of email software, from Outlook and Thunderbird to sendmail and Exchange, which seems a bit unlikely.

The subdomain trick I described works right now with all existing mail software. Anyone who used it to "port" an address would require configuration changes in their MTA and DNS, but that's orders of magnitude less work, and only affects the recipient mail hosts that support porting.

(by John L 28 Apr 2010 14:14)

Services like (I believe) and (which is what I'm using, since 1996) give you an address without a mailbox. All you get is a .forward (to use old-skool terminology) and you point it to where-ever your real mailbox happens to be this month. Works like a charm. I'm hardly imagining this is what the Knesset would like to propose, but it's a workable and fairly elegant solution.

(by era 03 May 2010 09:30)

Add your comment...

Note: all comments require an email address to send a confirmation to verify that it was posted by a person and not a spambot. The comment won't be visible until you click the link in the confirmation. Unless you check the box below, which almost nobody does, your email won't be displayed, and I won't use it for other purposes.

Email: you@wherever (required, for confirmation)
Title: (optional)
Show my Email address
Save my Name and Email for next time


My other sites

Who is this guy?

Airline ticket info

Taughannock Networks

Other blogs

Experian gets a slap on the wrist
48 days ago

A keen grasp of the obvious
Italian Apple Cake
384 days ago

Related sites

Coalition Against Unsolicited Commercial E-mail

Network Abuse Clearinghouse

© 2005-2020 John R. Levine.
CAN SPAM address harvesting notice: the operator of this website will not give, sell, or otherwise transfer addresses maintained by this website to any other party for the purposes of initiating, or enabling others to initiate, electronic mail messages.