toad.com open mail server

So there was some controversy decades ago the past about John Gilmore's public open SMTP relay server. I wondered if it still existed.

It does!

benc@dogger:~$ telnet new.toad.com 25
Trying 209.237.225.253...
Connected to new.toad.com.
Escape character is '^]'.
220 new.toad.com ESMTP Sendmail 8.12.9/8.12.9; Sun, 5 Mar 2017 08:12:44 -0800
EHLO dogger.cqx.ltd.uk
250-new.toad.com Hello dynamic-91.hawaga.org.uk [90.155.94.91] (may be forged), pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE 89000000
250-DSN
250-ETRN
250-AUTH GSSAPI
250-STARTTLS
250-DELIVERBY
250 HELP
MAIL FROM:benc@hawaga.org.uk
250 2.1.0 benc@hawaga.org.uk... Sender ok
RCPT TO:benc@hawaga.org.uk
250 2.1.5 benc@hawaga.org.uk... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
Subject: test 1

test
.
250 2.0.0 v25GCiXw019546 Message accepted for delivery
221 2.0.0 new.toad.com closing connection

Return-Path: 
Received: from new.toad.com (new.toad.com [209.237.225.253])
    by smtp-in.biscay.cqx.ltd.uk (8.14.4/8.14.4/Debian-2ubuntu2.1) with ESMTP id v25F9dpo009917
    for <benc@hawaga.org.uk>; Sun, 5 Mar 2017 15:09:40 GMT
Received: from dogger.cqx.ltd.uk (dynamic-91.hawaga.org.uk [90.155.94.91] (may be forged))
    by new.toad.com (8.12.9/8.12.9) with ESMTP id v25F96Xw016104
    for benc@hawaga.org.uk; Sun, 5 Mar 2017 07:09:28 -0800
Date: Sun, 5 Mar 2017 07:09:06 -0800
From: benc@hawaga.org.uk
Message-Id: <201703051509.v25F96Xw016104@new.toad.com>
Subject: test 1

email addresses are half case sensitive

The left hand part of an email address, the bit before the @ is case sensitive, in email in general. I've known that for a while - it seems to be an obscure-ish part of SMTP folklore.

Individual mail domains are perfectly at liberty to fold multiple distinct addresses into one, in their own domain, which is what most mail systems do: BENC and benc and bEnC all go to the same place @hawaga.org.uk. This leads many people to think that the left hand side is case insensitive.

This is just as they are at liberty to do that folding in other ways: for example, gmail ignores . in addresses, giving me b.clifford@gmail.com and bclifford@gmail.com. As well as b.c.l.i.ff.o.r.d@gmail.com

This came up on a mailing list (for browserid) that I watch, and I ended up being challenged in private email to cite a source. Luckily there's plenty of stuff around. RFC2821 section 2.4 seems to be the authority: The local-part of a mailbox MUST BE treated as case sensitive.

In the preparation of this blog post, I discovered something I didn't know before. It seems you cannot have multiple dots in a row in a plain email address. The RFC2821 production rules are:

      Local-part = Dot-string / Quoted-string
            ; MAY be case-sensitive

      Dot-string = Atom *("." Atom)

      Atom = 1*atext

where atext seems to come from the companion RFC2822 section 3.2.4. So b...clifford@gmail.com is not a valid address. Shame.