Re: [fetchmail-devel] fetchmail 6.3.15-beta1 beta release with "bad-header pass" feature

[Frédéric M. <fre...@wo...>]

On Thursday 25 February 2010, grarpamp wrote:
> >>> fetchmail.  This beta1 has the long-desired feature to ignore bad
> >>> headers in messages and pass them on.
>
> Hi group.
> What are 'bad headers'?
> Certainly would not all inbound headers be passed through fetchmail
> to disk or pipe, etc?

The purpose of this option is to ignore the invalid header lines if the server 
on which we are fetching the mail accepted (or even produced) that mail in 
the first place. If the mail can be delivered properly, everybody will be 
happy. If it can't, let's the blame fall on the software that can't handle it 
properly :-).

For instance, a mail header containing a very long line, was wrapped 
improperly by a previous version of my mail server. That is, the continuation 
line didn't start with a space. That invalid continuation line was then seen 
as an invalid mail header and fetchmail used to reject the whole mail as 
invalid. The mail was therefore undeliverable even though any other link in 
the mail delivery chain would have ignored that header just fine and passed 
the mail along. Returning it to the sender was dangerous (as the source 
address might have been forged) so the mail was stuck on the server.

With the new option, you can choose to reject any such mail as it used to be 
and avoid any trouble with the MDA/MTA to which fetchmail is passing the 
mail.

On the other hand, if you know the mail will be delivered without any problem, 
you can let it go and avoid to loose any mail.

Frederic