[exim] Re: Looking for advice on Grey Listing vs outlook.com…

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Author: Evgeniy Berdnikov
Date:  
To: exim-users
Subject: [exim] Re: Looking for advice on Grey Listing vs outlook.com's behaviour
On Tue, Aug 22, 2023 at 10:17:52AM +0200, Mark Elkins via Exim-users wrote:
> However, emails via Microsoft will keep changing the identity of the
> SMTP_Relay to a group of 10 or so SMTP Servers, so the initial delay keeps
> getting implemented ==> Customers complain.

...
> 3 - White list all the Outlook.com SMTP Server addresses - do they though
> remain static?


Do not rely on their static nature, I'm sure they aren't static.

Technically, you can retrive SPF record of sender (with Exim's lookup
of "dns" type), and scan it for "outlook.com" and "microsoft.com".
If some substring found, exclude greylisting.

% host -t txt outlook.com.
outlook.com descriptive text "v=spf1 include:spf-a.outlook.com include:spf-b.outlook.com ip4:157.55.9.128/25 include:spf.protection.outlook.com include:spf-a.hotmail.com include:_spf-ssg-b.microsoft.com include:_spf-ssg-c.microsoft.com ~all"
...
--
Eugene Berdnikov

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