Linux mail sends an email stat = sent but does not receive it.

Linux mail sends an email stat = sent but does not receive an email. Today, I try to use the mail command (e. g: mail-s "hello" xxx@163.com) to me 163.com mailbox, 163.com can not receive, however, you can always find the email I just sent under/var/mail/root. In fact, this is because the email failed to be sent, and sendmail rolled back the email. Check/var/log/maillog: Aug 1 18:41:40 localhost sendmail [5279]: o71Afeih005279: from = root, size = 220, class = 0, nrcpts = 1, msgid = <201008011041.o71Afeih005279@localhost.localdomain>, relay = root @ localhost Aug 1 18:41:42 localhost sendmail [5281]: o71Afekr005281: from = <root@localhost.localdomain>, size = 480, class = 0, nrcpts = 1, msgid = <201008011041.o71Afeih005279@localhost.localdomain>, proto = ESMTP, daemon = MTA, relay = localhost [127.0.0.1] Aug 1 18:41:42 localhost sendmail [5279]: o71Afeih005279: to = favorite214@139.com, ctladdr = root (0/0), delay = 00:00:02, xdelay = 00:00:02, mailer = relay, pri = 30220, relay = [127.0.0.1] [127.0.0.1], dsn = 2.0.0, stat = Sent (o71Afekr005281 Message accepted for delivery) Aug 1 18:41:44 localhost sendmail [5283]: o71Afekr005281: to = <favorite214@139.com>, ctladdr = <root@localhost.localdomain> (0/0), delay = 00:00:03, xdelay = 00:00:02, mailer = esmtp, pri = 120480, relay = mx.139.com. [221.176.6.96], dsn = 5.0.0, stat = Service unavailable Aug 1 18:41:44 localhost sendmail [5283]: Failed: DSN: Service unavailable Aug 1 18:41:44 localhost sendmail [5283]: o71Afikr005283: to = <root@localhost.localdomain>, delay = 00:00:00, xdelay = 00:00:00, mailer = local, pri = 31717, dsn = 2.0.0, stat = Sent later found a lot on google, finally, I found the cause: I fixed the problem by changing the hostname of my server. apparently "localhost. localdomain "will get rejected automatically by a lot of mail servers. as soon as I changed my hostname to "extra.idahostatesman.com" (a domain that is hosted on the server), everything just worked and I had no more problems sending e-mail. you can use the hostanme command to temporarily modify the host name, hostname aa.com; or failed Aug 1 19:11:33 localhost sendmail [5579]: o71BBVB9005579: from = root, size = 221, class = 0, nrcpts = 1, msgid = <201008011111.o71BBVB9005579@aa.com>, relay = root @ localhost Aug 1 19:11:35 localhost sendmail [5580]: o71BBX3b005580: from = <root@aa.com>, size = 436, class = 0, nrcpts = 1, msgid = <201008011111.o71BBVB9005579@aa.com>, proto = ESMTP, daemon = MTA, relay = localhost [127.0.0.1] Aug 1 19:11:35 localhost sendmail [5579]: o71BBVB9005579: to = favorite214@139.com, ctladdr = root (0/0), delay = 00:00:04, xdelay = 00:00:02, mailer = relay, pri = 30221, relay = [127.0.0.1] [127.0.0.1], dsn = 2.0.0, stat = Sent (o71BBX3b005580 Message accepted for delivery) Aug 1 19:11:39 localhost sendmail [5582]: o71BBX3b005580: to = <favorite214@139.com>, delay = 00:00:04, xdelay = 00:00:04, mailer = esmtp, pri = 120436, relay = mx.139.com. [221.176.6.96], dsn = 4.0.0, stat = Deferred: 450 Requested action not taken: cmcmx01, AS0QrJA75wiRVlVMWIvlAA --. 3152S2, dynamic, reputation, zen.spamhaus.org, please try again Remember: After modifying the hostname, You need to restart the sendmail service. After restarting the service, everything is OK.