how to identify smtp servers for a domain?

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how to identify smtp servers for a domain?

Juan Miscaro-2
Hi,

I'm trying to whitelist servers for a domain.  I know how to find MX
servers (what server to send mail to for that domain) but many
organizations use separate servers to send their mail.  How do I find
those sending (SMTP) servers so I can whitelist them?

/juan
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Re: how to identify smtp servers for a domain?

Arturo 'Buanzo' Busleiman
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Juan Miscaro wrote:
| I'm trying to whitelist servers for a domain.  I know how to find MX
| servers (what server to send mail to for that domain) but many
| organizations use separate servers to send their mail.  How do I find
| those sending (SMTP) servers so I can whitelist them?

They might be listed in the TXT record, inside SPF:

host -t txt somedomain.com

But you should use SPF, then...

- --
Arturo "Buanzo" Busleiman
Reliable inter-continental Mail Relay Service - Ask me!
Independent Security Consultant - SANS - OISSG
http://www.buanzo.com.ar/pro/
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Re: how to identify smtp servers for a domain?

Wietse Venema
In reply to this post by Juan Miscaro-2
Juan Miscaro:
> Hi,
>
> I'm trying to whitelist servers for a domain.  I know how to find MX
> servers (what server to send mail to for that domain) but many

MX servers RECEIVE mail for domains. They don't have to be the
same as the machines that SEND mail for a domain.

There is a protocol called SPF that identifies sending machines,
but only a minority of sites announces SPF records.

        Wietse

> organizations use separate servers to send their mail.  How do I find
> those sending (SMTP) servers so I can whitelist them?
>
> /juan
>
>

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Re: how to identify smtp servers for a domain?

Terry Carmen
In reply to this post by Juan Miscaro-2
Juan Miscaro wrote:
> Hi,
>
> I'm trying to whitelist servers for a domain.  I know how to find MX
> servers (what server to send mail to for that domain) but many
> organizations use separate servers to send their mail.  How do I find
> those sending (SMTP) servers so I can whitelist them?
>  
The only reliable way I'm aware of is to ask the admin for the domain.

This generally works well for smaller companies, but seems to be useless
for big operations like Yahoo, Microsoft, etc.

Terry


Terry

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