On 12/02/03 at 09:01, Chris Wagner wrote:Cool. That makes sense.
A couple of questions.
First, what is the HELO command and who is it issued by, the sending or receiving server, or both?
HELO (or EHLO) is issued by the sending MTA and is usually the first command issued after a connection is established. It's essentially the sending MTA introducing itself to the receiver and the command's argument is supposed to be (but isn't always) the sending MTA's host name. The HELO command should look something like:
HELO mail.senders.domain
That said, is it necessary that I contact them about this, or is it an internal issue with SIMS?09:06:13 3 SMTP-099(nekatech.net) Failed to get IP addresses. ErrorCode=-3170
09:06:13 3 SMTP-099(nekatech.net) No relay address is accessable. Error Code=-3170Error
09:06:13 3 SMTP [S.0000305454] dequeueing
09:06:13 1 SYSTEM(SMTP) [S.0000305454] failed on (nekatech.net)santes.
Code=-15001Error
09:06:13 1 SYSTEM(SMTP) [S.0000305454] failed on (nekatech.net)tball.
Code=-15001
SIMS is trying to send a message to two addresses (santes and tball) at
nekatech.net, but can't find an MX to send to. This is a DNS problem. (An
MX query from my machine here returns ex-neka.nekatech.net. which, in turn,
resolves to 63.168.156.20)
I guess I was thinking from what it sounded like in your reply that it was a problem with the MX (or lack of) record for their domain. Is this just an instance where whatever DNS server that points to their domain doesn't have an associated MX record for it?
I just want to make sure that I understand how SIMS works.OK.
So when you send a message through a SIMS box, it checks to make sure that:
1. The sender is in the client hosts list;
Yes, but only if 'Relay for Clients Only' is checked and only if the
message is to be relayed to some other MTA rather than delivered to a local
account. Note that the 'sender' here is the IP address of the machine that
has connected to SIMS.
Cool. That answers a bunch of questions.
2. The sender has an active account on the SIMS box;
No. Client hosts and local user accounts are two different things. If
'Advertise AUTH Capability' is enabled, the sender can use SMTP AUTH to
authenticate itself as a valid user and override the 'Relay for Clients
Only' check, but SIMS doesn't look at the sender's e-mail address other
than to verify that its the domain part is an existing domain name (if
'Verify Return-Paths' is checked).
3. The SIMS box can issue a greeting to the recipient's mail server;Thanks. I'm going to print that one for future reference (like to read in a few minutes....)
In a general sense, yes. As with any other command it sends in an SMTP session, if SIMS' HELO/EHLO gets a response from the remote MTA that indicates some sort of error, SIMS will end the session if appropriate to the error.
Just to be clear, the actions in (1) and (3) would take place in different SMTP sessions: the first when the message is sent to SIMS to be relayed (sender connects to SIMS) and the second when SIMS relays the message to its recipient (SIMS connects to recipient's MTA). In the first, SIMS is the receiver; in the second, SIMS is the sender.
I know there is more to it, but if anyone can point me to an RFC to
read the specific commands, I'd appreciate it.
RFC 821 (<http://www.faqs.org/rfcs/rfc821.html>) defines the SMTP protocol. There are more recent RFC's that modify and extend it, but 821 establishes the basics.
Thanks again for the response, Christopher.
Chris
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