Bind9 MX - how to change?

Question

Domain Name System

Good afternoon! I tried to add MX records to bind9, they didn’t exist before and everything worked (except for one of the mail servers where our messages did not reach, in connection with this I start adding MX) The
config is as follows:

@ IN SOA ns1.***.su. it.***.su. (
2011053102 ; serial
10800 ; refresh (3 hours)
900 ; retry (15 minutes)
604800 ; expire (1 week)
10800 ; minimum (3 hours)
)
@ IN A 91.***
@ IN NS ns1.***.su.
ns1 IN A 91.***
ns2 IN A 91.***

www IN CNAME ***.su.
mail IN CNAME ***.su.
www.mail IN CNAME ***.su.

Everything was ok with him, I started adding the following lines to the config: @ IN MX 10 ***.su.
I changed these MX records several times with every reload of bind9. After n number of MX entries, I don't receive mail from outside. Even if I return the config back to what it was, it doesn’t work ... I
check it through the dig online service, it gives the following:

;; QUESTION SECTION:
;***.su.			IN	MX

;; ANSWER SECTION:
***.su.		12940	IN	MX	10 ***.su.***.su.

Where does he get these records from? I don't have it in my config.
If I execute on my server: dig ***.su
There is not a word about MX records

Answer 1

serial changed?