Re: [exim] Cannot send mails to @hotmail.com addresses

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Author: Marc Sherman
Date:  
To: exim-users
Subject: Re: [exim] Cannot send mails to @hotmail.com addresses
Mike Cardwell wrote:
>
> I've found a way around their stupid filters. Well, it works for me
> anyway. Just before the dnslookup router create another router:
>
> This adds lots of large headers to the email message which seems to
> push the message size above a limit somewhere around 50KB at which
> point hotmail stops blackholing my mail. Maybe they don't perform
> certain scans on messages above a certain size.


Wow, that's a skanky hack. I love it!

> 4.) Hotmail doesn't blackhole any replies to mail afaics. With a
>     bit of testing I've found that whenever you send an email from your
>     hotmail account they record the Message-ID with the account. Any email
>     that you send back to that account will get through if the Message-ID is
>     valid. This means we could simply not apply the padding if an email
>     contains a message id of the correct format


I've also heard rumours (but I can't recall where I read them) that they
don't blackhole mail sent with Outlook, but they do blackhole mail sent
with Thunderbird. I guess there would exist a set of header
transformations we could apply in a router to fake that out, too.

I'm not currently motivated to spend the time finding out what those
transformations are, though, since my only client who was forwarding her
mail to hotmail has gotten a more reliable mailbox provider.

- Marc