Postfix Mail Error / Mail to local domain from local domain is qued

I've been having some issues with mail being sent to the local domain being qued - and when I view the mail que, its' showing up two errors -
1. Emails being sent to "root" - come up with the message = "user unknown"
2. Emails being send to user@domain.com from user2@domain.com - where domain.com (is the local domain configured on the server) are coming up with a message = "mail system configuration error"

My postfix main.cf is as follows -

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
anvil_rate_time_unit = 3600s
broken_sasl_auth_clients = yes
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
delay_warning_time = 4
disable_vrfy_command = yes
html_directory = no
inet_interfaces = all
local_recipient_maps =
mail_owner = postfix
mailbox_size_limit = 2048000000
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
message_size_limit = 204800000
milter_default_action = accept
milter_protocol = 2
mydestination = $myhostname, localhost.$mydomain, localhost
mydomain = example.com
myhostname = srv1.example.com
mynetworks = $config_directory/mynetworks
newaliases_path = /usr/bin/newaliases.postfix
non_smtpd_milters = $smtpd_milters
queue_directory = /var/spool/postfix
recipient_delimiter = +
relay_domains = proxy:mysql:/etc/postfix/mysql-relay_domains_maps.cf
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtp_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt
smtp_tls_session_cache_database = btree:$data_directory/smtp_tls_session_cache
smtp_use_tls = yes
smtpd_client_message_rate_limit = 500
smtpd_client_restrictions =
smtpd_data_restrictions = reject_unauth_pipelining
smtpd_helo_required = yes
smtpd_helo_restrictions =
smtpd_milters = inet:127.0.0.1:8891
smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination, reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_rbl_client zen.spamhaus.org, reject_rbl_client bl.spamcop.net, reject_rbl_client dnsbl.sorbs.net,check_policy_service unix:private/spfpolicy
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_path = private/auth
smtpd_sasl_security_options = noanonymous
smtpd_sasl_type = dovecot
smtpd_sender_restrictions =
smtpd_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt
smtpd_tls_cert_file = /etc/pki/tls/certs/srv1.example.com.crt
smtpd_tls_key_file = /etc/pki/tls/private/srv1.example.com.key
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_security_level = may
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
soft_bounce = yes
tls_random_source = dev:/dev/urandom
transport_maps = hash:/etc/postfix/transport
unknown_local_recipient_reject_code = 550
virtual_alias_maps = proxy:mysql:/etc/postfix/mysql-virtual_alias_maps.cf, regexp:/etc/postfix/virtual_regexp
virtual_gid_maps = static:12
virtual_mailbox_base = /var/vmail
virtual_mailbox_domains = proxy:mysql:/etc/postfix/mysql-virtual_domains_maps.cf
virtual_mailbox_maps = proxy:mysql:/etc/postfix/mysql-virtual_mailbox_maps.cf
virtual_minimum_uid = 101
virtual_transport = dovecot
virtual_uid_maps = static:101

After a number of hours going through the server log as well as postfix documentation, the problem seems to have resolved now.
What I did - reloaded & restarted the postfix service a number of times, in addition to a single reboot of the server too (to resolve and lingering scripts).

This configuration now seems to work perfectly. Adding "dovecot_destination_recipient_limit = 1" in the main.cf finally resolved the mail receipt to multiple users on the same domain on the same server.

==== main.cf (location: /etc/postfix) ====
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
anvil_rate_time_unit = 3600s
broken_sasl_auth_clients = yes
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
delay_warning_time = 4
disable_vrfy_command = yes
dovecot_destination_recipient_limit = 1
html_directory = no
inet_interfaces = all
local_recipient_maps = virtual_mailbox_maps
mail_owner = postfix
mailbox_size_limit = 2048000000
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
message_size_limit = 204800000
milter_default_action = accept
milter_protocol = 2
mydestination = $myhostname, localhost.$mydomain, localhost
mydomain = yourdomainname.com
myhostname = srv1.yourdomainname.com
mynetworks = $config_directory/mynetworks
newaliases_path = /usr/bin/newaliases.postfix
non_smtpd_milters = $smtpd_milters
queue_directory = /var/spool/postfix
recipient_delimiter = +
relay_domains = proxy:mysql:/etc/postfix/mysql-relay_domains_maps.cf
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtp_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt
smtp_tls_session_cache_database = btree:$data_directory/smtp_tls_session_cache
smtp_use_tls = yes
smtpd_client_message_rate_limit = 500
smtpd_client_restrictions =
smtpd_data_restrictions = reject_unauth_pipelining
smtpd_helo_required = yes
smtpd_helo_restrictions =
smtpd_milters = inet:127.0.0.1:8891
smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination, reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_rbl_client zen.spamhaus.org, reject_rbl_c$
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_path = private/auth
smtpd_sasl_security_options = noanonymous
smtpd_sasl_type = dovecot
smtpd_sender_restrictions =
smtpd_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt
smtpd_tls_cert_file = /etc/pki/tls/certs/srv1.yourdomainname.com.crt
smtpd_tls_key_file = /etc/pki/tls/private/srv1.yourdomainname.com.key
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_security_level = may
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
soft_bounce = yes
tls_random_source = dev:/dev/urandom
transport_maps = hash:/etc/postfix/transport
unknown_local_recipient_reject_code = 550
virtual_alias_maps = proxy:mysql:/etc/postfix/mysql-virtual_alias_maps.cf, regexp:/etc/postfix/virtual_regexp
virtual_gid_maps = static:12
virtual_mailbox_base = /var/vmail
virtual_mailbox_domains = proxy:mysql:/etc/postfix/mysql-virtual_domains_maps.cf
virtual_mailbox_maps = proxy:mysql:/etc/postfix/mysql-virtual_mailbox_maps.cf
virtual_minimum_uid = 101
virtual_transport = dovecot
virtual_uid_maps = static:101

I encountered the same from past 2-3 days and the solution i found is the same as mentioned above. Adding "dovecot_destination_recipient_limit = 1" in the main.cf and restarting postfix delivered all mails stuck in the queue.

The detail button on each message in the queue had the error :mail system configuration error"

Technically I don't know what has changed and why do we need this setting now, as it was working just fine before.