Like I wrote yesterday that the email server was down, today it’s up again. My feeling was right, the error was not at my side. Error was happened in center DNS. Somebody accidentally made mistake when edit the dns record. I didn’t who’s that, hope that it was not myself.

Everything just work fine and I can sleep well tonight.

PS:
when set relayhost in postfix use IP don’t use hostname.
If hostname is used, it will be error with message “Name or service not known”.
At least it’s happen to me.