* Bruce Momjian wrote:

Thom Brown wrote:

Also:

SELECT alias, description, token FROM ts_debug('myname+prior...@gmail.com');

Yields:

    alias   |   description   |       token
-----------+-----------------+--------------------
  asciiword | Word, all ASCII | myname
  blank     | Space symbols   | +
  email     | Email address   | prior...@gmail.com
(3 rows)

The entire string I entered is a valid email address, and isn't
totally uncommon.  Shouldn't that take such email address styles be
taken into account?  The example above incorrectly identifies the
email address since the real destination address would most likely be
myn...@gmail.com.

I had no idea '+' could be part of an email address, and in fact it is a
modifier that is stripped off when delivering the email:

No, it's not. Strictly speaking, "+" is simply one of many characters that are valid in the local-part of an e-mail address according to RFC 2822 (and 822, which was even more lenient there). The plus sign does not have any intrinsic semantics, except that it is obviously different from any other character for purposes of comparing addresses.

Even among applications that make decisions based on the value of various parts of e-mail addresses (usually MTAs when forwarding messages), the only ones that should be assigning special meaning to the plus sign are the MTAs responsible for delivering messages to their recipients in the recipient domain. A database that is only used for storing such addresses definitely should not attempt to divine what the _sender_ of the message meant when he put that plus sign in, or what it might mean to the _recipient_, who has no control over what people use as addresses when they send him e-mail.

Plainly put, the local-part should be treated as opaque everywhere outside the "administrative scope" of the recipient, and if you don't know whether you are in that scope, you are not. Splitting the local-part into subparts based on arbitrary rules that have no actual knowledge of the policies in place at the organization that assigned the address can only be a mistake.

Of course, the application that is using the database is free to use a ts configuration that does assign such meaning, if it has a reason to do so.

Examples:

- chris+postgre...@chrullrich.net

  Looks like I have a dedicated folder for messages concerning
  PostgreSQL. Now, _I_ know that I do not have such a folder, and
  that the suffix is meaningless. Nobody else can know for sure.

- jane+j...@example.com

  What is this?

  - A special suffix that John uses when sending messages
    to Jane, so they are forwarded to her BlackBerry with high
    priority?
  - A folder for Jane's large collection of "Dear John" letters?
  - Or is it simply Jane's and John's everyday address?

(Disclosure: I am what might be called a "plus sign nut". I routinely complain to webmasters and such when their applications try to tell me that the plus sign is not allowed in e-mail addresses. If you think I feel too strongly about this, you are free to disregard my message.)

--
Christian


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