Exchange drop support for SMTP?

Question

I want to send email with Exchange by using telnet to port 25. Until two week ago I was able to, but now a "security fix" from Microsoft has removed this possibility.

When I try, I get this message:

421 4.3.2 Service not available, closing transmission channel

What can I do?

Answer 1

SMTP is the protocol that is used to receive email from the rest of the world so I doubt that Microsoft has dropped that. There must be some other misconfiguration on your server.

Try double-checking your relay-settings and the event-log on your exchange-server.

Answer 2

I would suspect that whoever is in charge of the server has configured it to require SMTP authentication before accepting messages for relaying.

Answer 3

I found the answer at website:

http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=2900802&SiteID=17

Thanks for your help!

Basically, this functionality was removed by default and it could be restored by means of an ad hoc configuration - but with no guarrantee that further "updates" break the system again. Thanks, Microsoft.

Answer 4

I use a service (Message Labs (ML)) to filter out all the spam. We got a new internet connection and in the process of re-configuring ML's inbound/outbound services to the new IP, I got an error. So, I tested it from external by telneting to the IP on port 25 and got the "421 4.3.2 Service not available, closing transmission channel" error. What I didn't realize at first was that the reason it failed was because I had set a specific grouping of IPs on the 2007 edge server receive connector (for the ML servers). So, I added my lan network & additionally another IP for the external host I was testing from and low and behold, I could connect from both.

What I figured was happening with ML was that their server that was testing the connectivity was on an address that was excluded from the edge server.

So, I removed my testing IPs and created a new, temporary, receive connector on the edge server, accepting from all addresses (0.0.0.0 - 255.255.255.255). I then submitted the change to ML again and guess what...this time they accepted it. Now, I'll simply remove the test receive connector and everything should be golden.