Author: Ted Roche
Posted: 2013-04-29 at 13:09:44
On Mon, Apr 29, 2013 at 1:29 PM, Ken Dibble <krdibble@stny.rr.com> wrote:
> For those of you who administer email servers that communicate with the
> internet:
>
> Is it standard SMTP procedure to send a test email to a sender's address
> to verify that the address is valid?
>
No, this is the first time I've heard of that. Wikipedia describes callback
validation [1] but this shouldn't actually result in an email saved.
> This, in my opinion, is an unfair and poor way to verify the sender's
> address.
>
Agreed.
> Would this still occur with IMAP? As I understand it, IMAP is a retrieval
> protocol, not a send protocol. But if an ISP offers IMAP, which, as I
> understand it, by default leaves messages on the server, then surely the
> ISP must anticipate that many mailboxes will be full and would have to use
> some other sender verification strategy.
>
IMAP and POP are a completely different technology, that for retrieving and
storing email. not sending it. They don't have to even be on the same
box(es) as the SMTP service. So, no IMAP would not make a difference.
I am not asking for a referral to some other email service provider.
>
Perhaps you should be. The problem is your service provider is using an
arcane methodology and, as most service providers are supplying gigabytes
for free as part of their service, perhaps it's time you reconsidered your
mail system design. At the very least, a stern discussion with them to see
if they can prevent their self-caused outages.
> I am trying to understand what the options are for sender verify and why
> people use them.
>
As explained in the Wikipedia article, they're trying to verify that mail
actually came from a real mailbox and not a made up fake spam one. However,
I have a hard time understanding how this is filling up a mailbox until the
storage capacity is pitifully low.
POP is not designed to retain mail on the server. The "retain for x days"
functionality was an after-thought and the implications not fully
understood. It would probably make more sense to retain email in-house or
with another server. You could put your own mail server in between the
users and the internet, and retain mail there, but that may just be
shifting the problem.
[1] http://en.wikipedia.org/wiki/Callback_verification
--
Ted Roche
Ted Roche & Associates, LLC
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