Form does not send mail

Environment
OS CentOS release 6.10 (Final)
Apache Server version: Apache/2.2.15 (Unix)
postfix 2.6.6

Obtain domain in Sakura
Web server only (AWS CloudFront+LB+LightSail, DNS: Route 53)
I used Sakura rental server (premium) for the mail.

Today, around 10 or so, we will change the A record and name server of the zone change to the VPS of the web server's Misakura
I sent an email from the email form on the web, but the email was not delivered successfully.

The maillog is as follows.

 Sep 29 12:48:44 tk2-405-XXXX postfix/pickup [11819]:43504420A4:uid=48 from=<[email protected]>
Sep 29 12:48:44 tk2-405-XXXXXX postfix/cleanup[12041]:43504420A4:message-id=<20180929034844.43504420A4@t k2-xxx-xxxxxx.vs.sakura.ne.jp>
Sep 29 12:48:44 tk2-405-XXXX postfix/smtp[12042]: warning: no MX host for xxxxxxxx.com has valid address record
Sep 29 12:48:44 tk2-405-XXXXXX postfix/smtp[12042]:430204634B:to=<[email protected]>,relay=none,delay=0,delays=0/0/0,dsn=5.4.4,status=bounded(Host or domain name not found.Name service=for AAA xxxxx.sakura.ne.jp.xxxxxxxx.com
Sep 29 12:48:44 tk2-405-XXXX postfix/qmgr [1474]:43504420A4:from=<[email protected]>,size=4501,nrcpt=1 (queue active)
Sep 29 12:48:44 tk2-405-XXXX postfix/qmgr [1474]:430204634B:removed

The settings around the domain have been changed to the following

▼ Current Domain Zone Settings

Entry name type data
 @   NS ns1.dns.ne.jp.
 NS ns2.dns.ne.jp.
 A Sakura VPS Server IP
 MX10@
 www CNAME@
 mail CNAME@
 ftp CNAME@

·The A record has been changed around 10:00 today.

▼ Current Name Server Settings

Name Server 1 NS1.DNS.NE.JP
Name Server 2 NS2.DNS.NE.JP
Name Server 3
Name Server 4

·I changed it to the above setting around 10 today.

When testing by assigning a domain by test to a server on the VPS I tested it before changing it today, but the email was delivered without any problems.

In addition to the above, we have done the following today.
·Change the A record of the test domain obtained in Sakura from the server IP of Sakura VPS
·Replace the SSL certificate of the web server built on Sakura VPS (change to production domain)

Is this a temporary problem during DNS propagation?
I would appreciate it if you could let me know if you know anything.

9 As of September 29th at 16:00
We are currently restoring the domain (zone, name server) to its original state because we are using it for commercial use and cannot leave it at fault for a long time.