telnet session

telnet smtp.<mydomain>.io 25
Trying 217.70.184.8...
Connected to relay.mail.gandi.net.
Escape character is '^]'.
220 relay.mail.gandi.net ESMTP Postfix
EHLO smtp.<mydomain>.io
250-relay4-d.mail.gandi.net
250-PIPELINING
250-SIZE 35651584
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
mail from:<philippe.<mydomain>.io>
250 2.1.0 Ok
rcpt to:<philippe.<mydomain>.io>
554 5.7.1 <unknown[YY.YYY.YY.YY]>: Client host rejected: Access denied

YY.YYY.YY.YY = Public IP of my dedicated server