Re: SMTP option for DHCPv6

In <[email protected]> Arnt Gulbrandsen <[email protected]> writes:

> Cristian Cadar writes:
>
>> do you think that the SMTP option for DHCPv6 will be used in the
>> future by the email clients?
>
> Unlikely. It (and the IPv4 option) is incompatible with SPF, and my
> bet is that SPF will prove stronger. (Oversimplifying, SPF is a hacky
> way to say "only these IP addresses may send mail from this domain".)

I do not think that SPF is necessarily incompatible with DHCP, but the
use of SPF does place restrictions on which domains you can use with
which MTAs/MSAs.

Configuring DHCP would require knowing which domains the DHCP clients
would most likely use, and the DHCP clients would have to know if they
are using atypical domains.


> To see why it's incompatible, suppose you take your laptop along to
> the IETF in Paris in two months, and that your company uses SPF at
> that time. At the IETF, the DHCP server will give you an IP
> address. Perhaps it also gives you an SMTP server. If your laptop that
> server, then anyone who checks SPF will see that the IETF conference's
> SMTP server is not allowed to send mail on behalf of netlab.nec.de.

Right.  In cases of roaming users such as above, it doesn't really
make much sense to supply an SMTP server via DHCP, and it doesn't make
much sense for DHCP clients to pay attention to the suggested SMTP
server.

However, if you are in a corporate environment, it may make a lot of
sense to make sure that all email being sent out of the business is
using approved domain names via approved MTAs.


-wayne