On Mon, Aug 26, 2013 at 8:44 AM, Matus UHLAR - fantomas
<uh...@fantomas.sk>wrote:
> At my former job (an ISP), I recommended users to use SMTP service from
> they
> e-mail providers, because
> - if someone gets paid for mail service, they should provide SMTP too and
> not leave the expense from spam and phish issues onto us
> - it's not possible to verify the sender when we do not have the mailboxes,
> so we can not authenticate and verify the mail address
> - the same applies about SPF and DKIM, only the mailbox provider can be
> responsible for them.
>
That's interesting, several external mail service providers recommend the
exact opposite, at least for stationary clients (home computers etc.).
One reason for this is that compromised computers can then effectively be
taken out of circulation by the ISP.
The ISP has the means to know exactly which customer it is that has a
compromised computer, and deal with it appropriately.
So while you, as an ISP, may not necessarily have been able to verify
senders, you had the effective means to deal with spammers and other,
criminal activity.
It is also quite sensible that e-mail is handled as close to the point of
origin as possible. External SMTP services should preferably be used when
roaming (in a broader sense than mobile phone roaming), since it has a
pretty high risk of reducing reliability and performance.
I understand your arguments, though, but even so, many of them can be
applied also to an external SMTP provider.
Ideally, there would be decent mechanisms in place, but there are not, and
things like SPF and DKIM regrettably do not matter at all in anti-spam
measures – lots of the spam I see at work pass SPF and DKIM validation.
--
Jan
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