Is your ISP blocking outgoing port 25?

Jack Bates jbates at
Thu Jun 18 21:38:45 UTC 2009

Christopher Morrow wrote:
> in all seriousness, most isp's (consumer provider folk) today do some
> form of blocking of port 25, if you are 'smart' enough to evade this
> sort of thing, then you can still do email/blah. 99.999% of users are:
> 1) not interested in bypassing it
> 2) not clued into what's going on
> 3) using webmail

I'd say 0.5% of my customer base contacts the helpdesk to setup auth and 
bypass tcp/25 blocks using tcp/587. Another 2% use my webmail offsite, 
and about 10% use webmail only (on my network or off).

Then there's those pesky gmail users. We should just block them. j/k :P

> Why is this debate still ongoing??

Because nanog is slow? Actually, I think the original poster was just 
curious as these days not much is said overly much outside of the "Die 
Spammer" threads in other venues.


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