[nzlug] Exim: Limiting outgoing connections on Debian

[Mark Foster]

On Thu, 5 Oct 2006, Steven Ellis wrote:

> Vik Olliver wrote:
>> On Thu, 2006-10-05 at 16:28 +1300, Leon Matthews wrote:
>>
>>> Afternoon folks.
>>>
>>> I'm trying to send a bunch of emails (like 70) with attachments using Exim4
>>> on Debian Sarge and am hitting SMTP timeouts.
>>>
>>
>> Could be that your smarthost is rejecting them as an anti-spam measure.
>> Can you do it by direct mailing?
>>
>
> Direct mailing is getting very hard in NZ. Most NZ dialup and ADSL IPs
> are now classed as potential SPAM sources by a lot of tools.
>
> Steve (who isn't happy about having to use a smarthost).


I seem to recall Steve and I having a disagreement over this ;-)

Direct-mailing is frowned upon unless you run a fixed-IP system on a 
commercial-grade (read: high end broadband (frame relay, ethernet) or 
telehoused type arrangement) IP block.

If you are a fixed-IP internet customer of a small business or residential 
nature then you can often get away with direct mailing, but may encounter 
problems in some cases.

If you're dynamic IP: not a chance in hell...

A few years ago I was reccomending that all except pure dynamic-IP hosts 
try direct mailing, now I go the other way and suggest that smarthosts are 
the way to go for all except those with the high-end links.  Too much of 
the mail coming out of customer-space is spam these days, you can't rely 
on it.

The suggestions posted around getting your mailer to use existing 
connections instead of opening new ones, are the 'right' fix for this 
situation.  You shouldn't be opening multiple simultaneous SMTP 
connections (ISPs like Xtra will throttle you at 2, I think) as this can 
cause a huge load on your smarthost.

Netiquette dictates that you set a reasonable threshold and then just let 
the mail flow out over whatever time is required.

Regards
Mark.

(Speaking from my experience in the ISP space... but only for myself.)