On 8/31/01 11:02 AM, "Andy Fragen" <[EMAIL PROTECTED]> wrote:
>>
>> Not if the ISP is blocking all mail server communication out of their
>> network except for its own mail servers. Picture yourself in a room with one
>> phone jack hardwired to a handset for you to make calls. Sure you can bring
>> your own handset into the room, but you won't be able to plug it in
>> anywhere.
>
> Is my understanding of sendmail incorrect? I thought it was able to take
> mail from the email client and essentially process through the net so that
> as long as I have a network connection I am my own mail server able to send
> directly to anyone else's mail server.
>
> Here's an update: Through the Verizon DSL connection I can send and receive
> mail normally. This means I can use smtp.earthlink.net to send mail. From
> another LAN, connected via a shared T1, I am not able to send mail using
> smtp.earthlink.net as I get a relaying denied error.
>
> The problem isn't being blocked out of the LAN to the internet, it's trying
> to send mail from my Earthlink account, which doesn't allow relaying through
> their servers. If my understanding of sendmail is correct, and it could be
> wrong. I can use it to listen to port 25 on my computer, or some other port,
> as my own personal smtp server and it will send the email forward as long as
> I have a connection to the net.
>
> Am I misunderstanding this?
A little. What CAN happen is that your ISP can set all of their routers to
block any traffic that is destined for ANY port 25 unless the traffic
originates on their mail server.
This effectively says that only mail to or from one of their servers can be
sent.
Even though your sendmail would accept the mail from your client, it would
need to make a connection to port 25 on the destination computer to deliver
the mail. If your ISP is blocking all TCP/IP packets desitined for port 25
(unless it's theirs), that connection will not happen.
As an example, Verizon, AT&T, and maybe some others have done this with port
80 (the www port) to keep the Code Red virus from spreading. This means
that people who host web sites on their home machines can't do it any more
unless they use a non-standard port.
I know verizon does NOT do this (as I use Verizon at home and I use my work
smtp server to send my mail).
Unless your ISP is doing this "blanket port 25 blocking" then it should
work.
Make sense?
-Steve
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