错误信息：
Delivery to the following recipient has been delayed:
[email protected]
Message will be retried for 1 more day(s)
Technical details of temporary failure:
DNS Error: 353969976 DNS type 'mx' lookup of domain.com responded with code NOERROR
353969976 DNS type 'aaaa' lookup of mail.domain.com.domain.com.br. responded with code NXDOMAIN
353969976 DNS type 'a' lookup of mail.domain.com.domain.com. responded with code NXDOMAIN
这是我的 DNS 区域（db.domain.com.conf）：
;
; BIND data file for domain.com
;
$TTL 3h
@ IN SOA ns1.domain.com. admin.domain.com. (
1 ; Serial
3h ; Refresh after 3 hours
1h ; Retry after 1 hour
1w ; Expire after 1 week
1h ) ; Negative caching TTL of 1 day
;
@ IN NS ns1.domain.com.
@ IN NS ns2.domain.com.
domain.com. IN MX 10 mail.domain.com.
domain.com. IN A 191.222.92.24
ns1 IN A 191.222.92.24
ns2 IN A 191.222.92.150
www IN CNAME domain.com.
mail IN A 191.222.92.24
ftp IN CNAME domain.com.