[Discuss] Mail loop advice?

[gaf at blu.org (Jerry Feldman)]

On 11/13/2013 08:08 AM, Daniel Barrett wrote:
> Seeking advice on terminating an email loop.
>
> A friend with an RCN account sent me an email with a very large
> attachment. My ISP's server bounced it back to him, and RCN then
> rebounced it. This produced an email loop that has been running for
> about a week, bombarding my friend's account. My ISP (hostdime.com) is
> responsive and has cleared the message from its mail queue several
> times on my request, while my friend has no visibility into what RCN
> is doing about it. (Their first-level helpdesk advised him to call
> Microsoft for Outlook help. Their second level helpdesk performed
> unknown tasks.)
>
> Limitations: I don't have root access to my (shared) server: it's a
> cpanel-based account. My ISP is not willing to change its global email
> setup (say, to autodelete all email matching a pattern I provide) for
> fear of impacting its other customers.
>
> So I configured my cpanel spamassassin component to delete all email
> from my friend (on my ISP's suggestion). This has not helped. I've
> just configured it to delete all email from *@rcn.com and *@*.rcn.com;
> however, I don't know if cpanel's spamassassin component kicks in
> before or after the server's rule to bounce large attachments.
>
> Grateful for ANY advice on solving this frustrating problem as a mere
> client of the two service providers. (Anybody have a technical contact
> at RCN?)
In general, and undelivered message will remain in the queue for up to
about 5 days (This is configurable, but if my memory serves me, the RFC
might specify the number of days). So eventually that email will be
purged from the queue. Basically, the ISP does not bounce a message
back, the MTA can reject a message for a number of reasons. Some of
these reasons are non-fatal, so the sending ISP will keep sending it
until it times out. Additionally, the frequency the ISP sends the
message back is typically every 4 hours (again configurable), but after
a number of rejects, the time interval becomes larger. Your MTA (eg
sendmail, postfix) has a header-checks script where it can delete or
reject certain messages. We do this on BLU.org for most messages from
overseas.

Also, in your case the server probably kicks in long before cpanel. I
think in your specific case, your ISP's rejection is being interpreted
by RCN as non-fatal, such as a mailbox full message.

-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix
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