Outlook for iPhone不審なアクセス

V1.3.8 Outlook for iPhoneでIMAP接続の設定をすると下記のようなログが表示された。

Sep 18 09:41:52 hogehoge.jp postfix/smtpd[54336]: connect from ec2-54-148-7-237.us-west-2.compute.amazonaws.com[54.148.7.237]
Sep 18 09:41:54 hogehogejp postfix/smtpd[54336]: verify password: AUTH LOGIN: authentication succeeded for user=xxxxxxxxxxxxxxxxxxxxxxxx
Sep 18 09:41:55 hogehoge.jp postfix/smtpd[54336]: disconnect from ec2-54-148-7-237.us-west-2.compute.amazonaws.com[54.148.7.237]

dovecotのログにもある。

# grep mailinglist /Library/Logs/Mail/mail-info.log
Sep 18 09:41:44 imap-login: Info: Login: user=<xxxxxxxxxxxxxxxxxxxxxxxx>, method=LOGIN, rip=54.148.7.237, lip=xxx.xxx.xxx.xxx, mpid=2170, TLS
Sep 18 09:41:45 imap(pid 2170 user xxxxxxxxxxxxxxxxxxxxxxxx): Info: Disconnected: Logged out in=9 out=490
Sep 18 09:41:57 imap-login: Info: Login: user=<xxxxxxxxxxxxxxxxxxxxxxxx>, method=LOGIN, rip=52.24.116.112, lip=xxx.xxx.xxx.xxx, mpid=2170, TLS
Sep 18 09:41:57 imap(pid 2170 user xxxxxxxxxxxxxxxxxxxxxxxx): Info: Disconnected: Logged out in=9 out=490