mailq 给了我这个错误：
F2E7B32820F3 3549 Wed Feb 17 12:15:50 "www-data@info"@hivemind.ru
(host mxs.mail.ru[94.100.180.150] said: 421 Problem resolving DNS for domain info"@hivemind.ru (Domain name is syntactically invalid) (in reply to MAIL FROM command))
我看到由同一软件（旧 SMF 论坛）生成的此类消息，但我找不到确切的消息。在互联网上搜索没有结果。
论坛软件似乎正确生成消息：
postcat -vq 0492D3282068
postcat: name_mask: all
postcat: inet_addr_local: configured 2 IPv4 addresses
postcat: inet_addr_local: configured 2 IPv6 addresses
*** ENVELOPE RECORDS maildrop/0492D3282068 ***
message_arrival_time: Sun Feb 21 15:01:55 2016
named_attribute: rewrite_context=local
sender_fullname: www-data
sender: www-data
*** MESSAGE CONTENTS maildrop/0492D3282068 ***
regular_text: To: test@example.com
regular_text: Subject: =?UTF-8?B?0JTQvtCx0YDQviDQv9C+0LbQsNC70L7QstCw0YLRjCDQvdCwINGE0L7RgNGD0LwgUFNZVFJJQkU=?= …