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#### 6.4.10 Washing Mail

Mailers and list servers are notorious for doing all sorts of really, really stupid things with mail. “Hey, RFC 822 doesn’t explicitly prohibit us from adding the string `wE aRe ElItE!!!!!1!!` to the end of all lines passing through our server, so let’s do that!!!!1!” Yes, but RFC 822 wasn’t designed to be read by morons. Things that were considered to be self-evident were not discussed. So. Here we are.

Case in point: The German version of Microsoft Exchange adds ‘`AW:` ’ to the subjects of replies instead of ‘`Re:` ’. I could pretend to be shocked and dismayed by this, but I haven’t got the energy. It is to laugh.

Gnus provides a plethora of functions for washing articles while displaying them, but it might be nicer to do the filtering before storing the mail to disk. For that purpose, we have three hooks and various functions that can be put in these hooks.

`nnmail-prepare-incoming-hook`

  This hook is called before doing anything with the mail and is meant for grand, sweeping gestures. It is called in a buffer that contains all the new, incoming mail. Functions to be used include:

  `nnheader-ms-strip-cr`

    Remove trailing carriage returns from each line. This is default on Emacs running on MS machines.

`nnmail-prepare-incoming-header-hook`

  This hook is called narrowed to each header. It can be used when cleaning up the headers. Functions that can be used include:

  `nnmail-remove-leading-whitespace`

    Clear leading white space that “helpful” listservs have added to the headers to make them look nice. Aaah.

    (Note that this function works on both the header on the body of all messages, so it is a potentially dangerous function to use (if a body of a message contains something that looks like a header line). So rather than fix the bug, it is of course the right solution to make it into a feature by documenting it.)

  `nnmail-remove-list-identifiers`

    Some list servers add an identifier—for example, ‘`(idm)`’—to the beginning of all `Subject` headers. I’m sure that’s nice for people who use stone age mail readers. This function will remove strings that match the `nnmail-list-identifiers` regexp, which can also be a list of regexp. `nnmail-list-identifiers` may not contain `\\(..\\)`.

    For instance, if you want to remove the ‘`(idm)`’ and the ‘`nagnagnag`’ identifiers:

        (setq nnmail-list-identifiers
              '("(idm)" "nagnagnag"))

    This can also be done non-destructively with `gnus-list-identifiers`, See Article Hiding.

  `nnmail-remove-tabs`

    Translate all ‘`TAB`’ characters into ‘`SPACE`’ characters.

  `nnmail-ignore-broken-references`

    Some mail user agents (e.g., Eudora and Pegasus) produce broken `References` headers, but correct `In-Reply-To` headers. This function will get rid of the `References` header if the headers contain a line matching the regular expression `nnmail-broken-references-mailers`.

`nnmail-prepare-incoming-message-hook`

  This hook is called narrowed to each message. Functions to be used include:

  `article-de-quoted-unreadable`

    Decode Quoted Readable encoding.

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