Mutt无法发送电子邮件Ubuntu 20.04

如何解决Mutt无法发送电子邮件Ubuntu 20.04

我正在尝试从终端向我发送mutt的电子邮件。发送电子邮件的热点是Digital Ocean中的Ubuntu 20.04的全新安装。 我只安装了mutt和sendmail并运行以下命令：echo "d" | mutt -d 1 -s "rere" -- [e-mail]，但是邮件从未到达我的收件箱（已检查垃圾邮件）。

调试信息根本对我没有帮助：

root@RayTracer:~# cat .muttdebug4
[2020-08-28 11:33:59] Mutt/1.13.2 (2019-12-18) debugging at level 1
[2020-08-28 11:35:00] mutt_free_body: unlinking /tmp/mutt-RayTracer-0-22282-3535318651879772016.
[2020-08-28 11:35:00] mutt_buffer_pool_free: 5 of 5 returned to pool

有什么解决方法吗？

编辑：看起来sendmail无效。调试信息：

root@RayTracer:~# tail /var/log/mail.err
Aug 28 12:01:01 RayTracer sm-msp-queue[23723]: unable to qualify my own domain name (RayTracer) -- using short name
Aug 28 12:04:30 RayTracer sendmail[23826]: My unqualified host name (RayTracer) unkNown; sleeping for retry
Aug 28 12:05:30 RayTracer sendmail[23826]: unable to qualify my own domain name (RayTracer) -- using short name
Aug 28 12:06:53 RayTracer sendmail[23900]: My unqualified host name (RayTracer) unkNown; sleeping for retry
Aug 28 12:07:53 RayTracer sendmail[23900]: unable to qualify my own domain name (RayTracer) -- using short name
Aug 28 12:13:06 RayTracer sendmail[24025]: My unqualified host name (RayTracer) unkNown; sleeping for retry
Aug 28 12:14:06 RayTracer sendmail[24025]: unable to qualify my own domain name (RayTracer) -- using short name
Aug 28 12:15:39 RayTracer sm-mta[24092]: 07SCFdCZ024092: SYSERR(root): localhost.localdomain. config error: mail loops back to me (MX problem?)
Aug 28 12:18:07 RayTracer sm-mta[24154]: 07SCI7x7024154: SYSERR(root): localhost.localdomain. config error: mail loops back to me (MX problem?)
Aug 28 12:19:42 RayTracer sm-mta[24206]: 07SCJgnZ024206: SYSERR(root): localhost.localdomain. config error: mail loops back to me (MX problem?)

在我尝试通过如下修改mail loops back to me文件来解决unqualified host name错误之后，开始出现/etc/hosts错误：

# Your system has configured 'manage_etc_hosts' as True.
# As a result,if you wish for changes to this file to persist
# then you will need to either
# a.) make changes to the master file in /etc/cloud/templates/hosts.debian.tmpl
# b.) change or remove the value of 'manage_etc_hosts' in
#     /etc/cloud/cloud.cfg or cloud-config from user-data
#
127.0.1.1 RayTracer RayTracer
127.0.0.1 localhost.localdomain localhost RayTracer