smtp no any error return?

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smtp no any error return?

Post by jin » 2019-05-13 05:18

I write a edm client using C# SmtpClient
code like
SmtpClient smtp = new SmtpClient();
smtp.Host = "hmailserver ip";
smtp.Port = 25;

catch (Exception ex)

if recipient email address is <--- domain not exists, success <--- domain exists, but account not exists, still success
xxx@xxx <--- not valid mail address , success
xxxxx <--- error

what can i do to get real smtp error ??

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Re: smtp no any error return?

Post by Dravion » 2019-05-13 06:15

hMailServer implements the IETF RFC5321 SMTP Implementation Specifications.
There are Replycode specific Categories as follows:
There are four values for the first digit of the reply code:

2yz Positive Completion reply
The requested action has been successfully completed. A new
request may be initiated.

3yz Positive Intermediate reply
The command has been accepted, but the requested action is being
held in abeyance, pending receipt of further information. The
SMTP client should send another command specifying this
information. This reply is used in command sequence groups (i.e.,
in DATA).

4yz Transient Negative Completion reply
The command was not accepted, and the requested action did not
occur. However, the error condition is temporary, and the action
may be requested again. The sender should return to the beginning
of the command sequence (if any). It is difficult to assign a
meaning to "transient" when two different sites (receiver- and
sender-SMTP agents) must agree on the interpretation. Each reply
in this category might have a different time value, but the SMTP
client SHOULD try again. A rule of thumb to determine whether a
reply fits into the 4yz or the 5yz category (see below) is that
replies are 4yz if they can be successful if repeated without any
change in command form or in properties of the sender or receiver
(that is, the command is repeated identically and the receiver
does not put up a new implementation).

5yz Permanent Negative Completion reply
The command was not accepted and the requested action did not
occur. The SMTP client SHOULD NOT repeat the exact request (in
the same sequence). Even some "permanent" error conditions can be
corrected, so the human user may want to direct the SMTP client to
For further Information read the RFC

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