Re: [tlug] B Flets blocks port 25?

[Curt Sampson <cjs@example.com>]

On 2008-05-29 12:56 +0900 (Thu), Hung Nguyen Vu wrote:

> Is that my provider blocks port 25 and I can't send outgiong emails?

Yes.

On 2008-05-29 13:31 +0900 (Thu), Hung Nguyen Vu wrote:

> It uses relayhost provided by the ISP.

That should work.

On 2008-05-29 13:06 +0900 (Thu), Drew Hamilton wrote:

> Most providers in Japan block 25 outbound on residential service
> nowadays.

Right. Over the past year or so, many providers, if what I've been
seeing is any indication, are doing this.

On 2008-05-29 21:07 +0900 (Thu), Dave Brown wrote:

> Really, blocking outbound SMTP to everything but the ISP's SMTP host
> only makes sense.

Indeed. One of the big reasons for taking over a random (usually
Windows) machine on a DSL or similar connection is to send spam mail. So
many trojans, viruses, etc. these days are careful not to do damage to
the computer that they take over, or even provide any hint that they've
taken it over, because it's quite useful for sending spam, participating
in denial of service attacks, and so on. Should you desire to do a
similar thing yourself, these folks will rent to you their network of
taken-over computers (referred to as a "botnet") for a reasonable price.

ISPs tend to block various other ports on "consumer-grade" connections
as well, especially the SMB and NMBD ports used by Microsoft's file
sharing services, the idea being to protect users who just happen to
have unwittingly shared their whole drive with the world.

Keep in mind, too: even if the ISPs still were allowing outbound port
25, most of these addresses are in lists that people maintain of
consumer-level connections (for the pros here, I mean DUL-type stuff)
that many people use on their mail servers as lists of addresses from
which to block mail connections.

If you want to run your own mail server, one option is to get an account
from Asahi-Net, and pay an extra 800 yen per month (or whatever it is)
for the static IP address option (which requires you to authenticate
with an "f." before your account name). They don't block port 25 in
either direction there, and appear not to have any intent to do so.

(This service used to be free, by the way, and not changing the IP
address costs them nothing, but having run an ISP myself, I'd venture to
say that the 800 yen a month is probably about covering the additional
technical support costs and other risks, and this isn't a profit centre
for them.)

By the bye, has anybody noticed that Asahi-Net over B-Flets seems a bit
slow? Even within Tokyo, I seem to get only about 13-15 Mbps, whereas
between a couple of Usen-connected hosts, I get 60-80 Mbps. I'd love to
hear where else I could go to get a static IP, without filtering, that
offers better performance.

Or, for that matter, I'm willing to pay a couple man en per month for
a /29 that gives good performance. Feel free to reply privately or
publically.

(And hey, if I can find someone to route my /24, which is old and low
enough to be a global prefix, now you're talking....)

cjs
-- 
Curt Sampson       <cjs@example.com>        +81 90 7737 2974   
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