Connection timed out (?)

This is happening only toward a specified recipeint. Whenever i send a mail with my fortimail in gatweay mode the recipient server is always in connection timeout. If i send the same mail using postifix or another mail relay it is sent. This is the error message : " timeout waiting for input from mail.xxxxxxx.com. during client greeting" Their system administrator told me to change this, but i can' t find the fortimail option where to change it: " http://www.ietf.org/rfc/rfc2821.txt …”Based on extensive experience with busy mail-relay hosts, the minimum per-command timeout values SHOULD be as follows: Initial 220 Message: 5 minutes An SMTP client process needs to distinguish between a failed TCP connection and a delay in receiving the initial 220 greeting message. Many SMTP servers accept a TCP connection but delay delivery of the 220 message until their system load permits more mail to be processed.”... "