$ dig mx andowson.com
; <<>> DiG 9.2.4 <<>> mx andowson.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24079
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 8, AUTHORITY: 2, ADDITIONAL: 0
;; QUESTION SECTION:
;andowson.com. IN MX
;; ANSWER SECTION:
andowson.com. 604800 IN MX 10 aspmx.l.google.com.
andowson.com. 604800 IN MX 20 alt1.aspmx.l.google.com.
andowson.com. 604800 IN MX 30 alt2.aspmx.l.google.com.
andowson.com. 604800 IN MX 40 aspmx2.googlemail.com.
andowson.com. 604800 IN MX 50 aspmx3.googlemail.com.
andowson.com. 3600 IN MX 60 220-135-57-87.hinet-ip.hinet.net.
andowson.com. 3600 IN MX 100 smtp.where.secureserver.net.
andowson.com. 3600 IN MX 200 mailstore1.secureserver.net.
;; AUTHORITY SECTION:
andowson.com. 3600 IN NS park29.secureserver.net.
andowson.com. 3600 IN NS park30.secureserver.net.
;; Query time: 558 msec
;; SERVER: 168.95.1.1#53(168.95.1.1)
;; WHEN: Wed Aug 29 08:01:55 2007
;; MSG SIZE rcvd: 317
申請了
Google Apps的郵件代管後, 在DNS上面設定MX順序時已把gmail放在上面了, 等於是Postfix對 andowson.com 的 MX 指到 gmail去了,因此信就往 gmail smtp跑, 而gmail smtp沒開放 open relay, 當然就寄不出去囉.