先感謝AdaHsu兄的回覆.

/var/log/maillog 裡的資訊寫到
localhost postfix/smtp [11066]: connect to gmail-smtp-in.l.google.com[64.233.183.114]: Connection timed out (port 25)

而可收到的信箱則是
localhost postfix/smtp[11066]: 1CABA38062: to=<user@company's domain name>, replay=sj - inbound-company's mail server name[ip address]:25, delay=3.1, delays=0.03/0.01/1.7/1.4, dsn=2.0.0, status=sent (250 ok: Message 103785113 accepted)

小弟有試過ping google的mail server,是有回應的.小弟在猜是否會在relay的過程中被擋掉了?