BS: Math / Email question

Subject: Math / Email question
From: GUEST,Peter Hazel
Date: 27 Feb 01 - 05:01 PM

This is pretty obscure and entirely irrelevant, but knowing Mudcat someone might know.

I have a domain where emails addressed to [e-mail] get delivered to my normal email address. I'm told that this offers me 'an infinite number of email addresses'

Is this true? Is there a limit to the number of characters that can be placed before the @ sign. I imagine there must be, I cant imagine that I could have a 5 million character name, but I may be wrong.

The Math part of the query is, if the limit of characters before the @ sign is, say 256, how many email addresses could I have?

Peter

Subject: RE: BS: Math / Email question
From: mousethief
Date: 27 Feb 01 - 05:09 PM

the number of possible characters per position

+ 26 (A-Z, assuming it's not case-sensitive)
+ 10 (numerical digits)
+ 04 (period, hyphen, i'm not sure how many, let's say 4))
= 40,

raised to the power of the number of positions that you can have (256 in your example).

40^256. My calculator can't count that high.

Anyway that's how you figure it out.

Alex

Subject: RE: BS: Math / Email question
From: GUEST,Peter Hazel
Date: 27 Feb 01 - 05:19 PM

Thanks, Mousethief

You taught me something.

I used 256 as an example as it's the maximum length of a file name in Windows.

I'd be interested to know if there are any such restrictions regarding email addresses.

Peter

Subject: RE: BS: Math / Email question
From: GUEST,Willa
Date: 27 Feb 01 - 05:36 PM

Peter Hazel Just as an example, if you only have 15 characters in front of the @ sign, 40^15 is 1.073741824 times 10^24, which should be enough to satisfy anyone!

Subject: RE: BS: Math / Email question
From: GUEST,Peter Hazel
Date: 27 Feb 01 - 05:42 PM

Willa,

Of course you are right.

I'm just curious as to whether 'infinite' actually means 'infinite' in it's truest sense.

Peter

Subject: RE: BS: Math / Email question
From: Mr Red
Date: 27 Feb 01 - 05:46 PM

I thought the limit on domain name characters was raised to 63 or 64 (2^6) last year. Wouldn't a similar limit or the same limit minus the number of characters in your domian name be the limit? It's all about packet size and address bytes.

So it's 40^(64-len(domainname)) = 8.307ish X 10^92 for my domain name cresby.com

Still mindbogglingly big.

Subject: RE: BS: Math / Email question
From: GUEST,Willa
Date: 27 Feb 01 - 05:55 PM

Peter Hazel Just as an example, if you only have 15 characters in front of the @ sign, 40^15 is 1.073741824 times 10^24, which should be enough to satisfy anyone!

Subject: RE: BS: Math / Email question
From: GUEST,Peter Hazel
Date: 27 Feb 01 - 05:55 PM

Mr Red,

Of course it's mind bogglingly big, and no one could have any use for it - everyone in the world would need to have ridiculous numbers of email addresses each.

I still want to know whether there's a 'maximum' character length for email addresses - purely an academic query.

Websites may be limited to 64, is that the same with email?

Peter

Subject: RE: BS: Math / Email question
From: mousethief
Date: 27 Feb 01 - 06:09 PM

Anyway, it's not infinite, but for all practical purposes it's close enough to infinite as makes no never-mind, as my grandmother would say!

Alex

Subject: RE: BS: Math / Email question
From: GUEST,Peter Hazel
Date: 27 Feb 01 - 06:24 PM

Maybe I haven't made myself clear.

Of course, I can have more email addresses that I'd ever want or need (I use 3).

I'm interested in knowing whether there is a 'limit' in terms of email addresses - can i have an address with 5 million character before the @ or not?

An academic question, but one that I'd like to know the answer for

Subject: RE: BS: Math / Email question
From: mousethief
Date: 27 Feb 01 - 06:26 PM

Even if you could, nobody could send mail to it, since email reading/writing programs/websites have limits to the amount of characters you can stuff into the "to" field.

Subject: RE: BS: Math / Email question
From: GUEST,Bruce O.
Date: 27 Feb 01 - 06:28 PM

The number of atoms comprising plant earth is about 10^50. 40^256 is probably more than enough to number every atom in the known universe.

Subject: RE: BS: Math / Email question
From: GUEST,Peter Hazel
Date: 27 Feb 01 - 06:29 PM

So what is the limit?

Subject: RE: BS: Math / Email question
From: GUEST
Date: 27 Feb 01 - 06:39 PM

Who cares? Nobody's ever going to use even a very small fraction of all of them.

Subject: RE: BS: Math / Email question
From: GUEST
Date: 27 Feb 01 - 06:40 PM

Who cares? Nobody's ever going to use even a very small fraction of all of them.

Subject: RE: BS: Math / Email question
From: GUEST
Date: 27 Feb 01 - 06:42 PM

Does that mean you get everybody's email, and no one else gets any?

Subject: RE: BS: Math / Email question
From: GUEST
Date: 27 Feb 01 - 06:49 PM

No. To do that you'd have to have *@*.*.*

Subject: RE: BS: Math / Email question
From: Amos
Date: 27 Feb 01 - 08:45 PM

You need to go look up the original RFC on the basic mail protocol -- probably at Network Associates or do a search on RFC and go back into the archive. While the body of an email can be broken up into an indeterminate number of packets, using TCP/IP, and the IP number is a fixed length in the header of each packet, I don't know about the spec for alphanumeric domain names. Theproblem would not stem from email per se, because the IP number is sufficient to get it to the host that serves your mail and then the message could be parsed for whatever was on the left side of the '@' sign in the To: field. The problem would come from the dimensions allowed in DNS services, I would think, where your imaginary > 256 char string might exceed allocated space for the alphanumeric side of lookup table entries. So the data stored would be (perhaps) a truncated version which would never yield a hit. So the IP number would never get found and mail heading for you would perhaps bounce.

No, no no!!! Actually, that's all wrong -- the alphanumeric version of the domain is on the right side of the @ sign so that shorter part is what woudl be used to find the target host address. But in that mail server, you would be butting up against the string length max for the username list -- in a typical UNIX system the mapping of users to hosts. I don't know the details well enough as you can see -- ya needs a UNIX guru!

A