How can I make sure that after changing the IP of the domain name in the DNS (A) records to another server, mail continues to work on the old server?

Question

Domain Name System

Hello,
After I transferred the site to another server, mail stopped coming.
The remaining boxes whose IP mail server work fine. The server is running Postfix + dovecot. Sending mail works. Incoming calls don't arrive. mail.log does not give errors
I do not know how to google this question, tell me pliz.

my postfix config

# See /usr/share/postfix/main.cf.dist for a commented, more complete version


# Debian specific:  Specifying a file name will cause the first
# line of that file to be used as the name.  The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on
# fresh installs.
compatibility_level = 2



# TLS parameters
smtpd_tls_cert_file=/etc/letsencrypt/live/имя почтового сервера/fullchain.pem
smtpd_tls_key_file=/etc/letsencrypt/live/имя почтового сервера/privkey.pem
smtpd_tls_security_level=may
smtpd_tls_loglevel = 1
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache

smtp_tls_security_level=may
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_tls_loglevel = 1

smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtpd_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtp_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = "имя почтового сервера"
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = $myhostname, localhost.$mydomain, localhost
relayhost = 
mynetworks = 127.0.0.0/8
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
myorigin = /etc/mailname
mailbox_transport = lmtp:unix:private/dovecot-lmtp
smtputf8_enable = no
virtual_mailbox_domains = proxy:mysql:/etc/postfix/sql/mysql_virtual_domains_maps.cf
virtual_mailbox_maps =
   proxy:mysql:/etc/postfix/sql/mysql_virtual_mailbox_maps.cf,
   proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_mailbox_maps.cf
virtual_alias_maps =
   proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_maps.cf,
   proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_maps.cf,
   proxy:mysql:/etc/postfix/sql/mysql_virtual_alias_domain_catchall_maps.cf
virtual_transport = lmtp:unix:private/dovecot-lmtp
virtual_mailbox_base = /var/vmail
virtual_minimum_uid = 2000
virtual_uid_maps = static:2000
virtual_gid_maps = static:2000
policyd-spf_time_limit = 3600
smtpd_recipient_restrictions =
   permit_mynetworks,
   permit_sasl_authenticated,
   reject_unauth_destination,
   check_policy_service unix:private/policyd-spf
# Milter configuration
milter_default_action = accept
milter_protocol = 6
smtpd_milters = local:opendkim/opendkim.sock
non_smtpd_milters = $smtpd_milters

Answer 1

The problem was in the wrong hosts file of the new server, it contained the mail address.

Answer 2

configure MX record?