[Exim] Closed connection for different reason !

Hello,

I've a running Exim 4.12 since 24h, this config acts as un mailrelay for
external domains and smarthost for internal to domains.

Everything works good until the first "closed connection in response to
initial connection" error appears in the mainlog. Since that, many mail
are not deliveried because retry time not reached. If I decrease the
retry time interval the problem could be resolv but regularly the
"closed connection..." error occurs. What could be the reason of this
error ?

Also, I've for certain remote smtp server the following error : "Closed
connection in response to EHLO ...." ? But the error doesn't occurs
systematicaly with server ?

Thank you,

--
Raphaël Berghmans <rberghmans@???>