One of my clients has just advised me that they are not/ have not received email since last friday. Tuesday now although Monday was Holiday.
initially tried to telnet to server.
Mail From: ok.
rcpt to: No such user (or similar)
Checked the user existed and was not disabled. OK.
Checked services and restarted Exchange. OK. Still Failed
Rebooted Server. OK
Tried to telnet into server again.
mail from:email@example.com OK
Reponse takes about 1 min. Then all other commands complete successfully and quickly.
Tried to telnet with rcpt to 3rd party domain.
550 5.7.1 Unable to Relay for .... Again this took about 1 min to respond.
I saw a post that refered to RBLs. There are non configured.
client is running Trend WFBS. Latest version.
it appears to be a delay in the email address lookup to Active Directory maybe. But this is beyond my knowlede and need some help to confirm and fix.