I have qmail server , installed by qmailtoaster typically.
A few months running normally, but yesterday, suddenly qmail server cannot
receive messages from another servers.
I checked below:
1. On Sender mailserver , message cannot send to qmail ,and queued as:
Running /var/spool/mqueue/r119VbD2006876 (sequence 97 of 998)
<email@example.com>... Deferred: Connection reset by [qmail IP Addr]
2. Sender mailserver can send messages to another mailservers.
(It seems the sender mailserver is normally running)
3. On qmail server , domestic messages can send/receive.
4. from sender mailserver , manually send to qmail using telnet is
telnet [qmail server name] smtp
220 mydomain.com - Welcome to Qmail Toaster Ver. 1.3 SMTP Server ESMTP
It seems OK.
5.On qmail server , no rejected error logs in /var/log/qmail/smtp,send , /var/log/maillog
How can I investigate this problem?