How to prevent, or change priority, of dovecot's FAILed relay-submission to relay's IPv6 address, and submit ONLY/first to IPv4?

my server is a linux, dual-stack IPv4/IPv6 host

it runs multiple services, including, but not limited to, postfix & dovecot

the hostname is

internal.mx.example.com

its DNS config,

host internal.mx.example.com
	internal.mx.example.com has address 10.1.1.15
	internal.mx.example.com has IPv6 address fd80:10:1::15
	internal.mx.example.com mail is handled by 5 internal.mx.example.com.

here, for dovecot

dovecot --version
	2.3.13 (89f716dc2)

submission is configured to relay to the same-host postfix instance, listening @ port 465

./conf.d/10-master.conf
	...
	protocols = imap submission lmtp sieve
	...
	submission_relay_host       = internal.mx.example.com
	submission_relay_port       = 465
	submission_relay_ssl        = smtps
	submission_relay_ssl_verify = yes
	submission_relay_trusted    = yes

whereas other services listen at both IPv4 & IPv6 addresses, with IPv6 preferred over IPv4, postfix listens ONLY on IPv4,

postconf inet_protocols
	inet_protocols = ipv4

and, as intended, simply refuses ipv6 connections

telnet 10.1.1.15 465
	Trying 10.1.1.15...
	Connected to 10.1.1.15.
	Escape character is '^]'.
	^]
	telnet> quit
	Connection closed.

telnet -6 fd80:10:1::15 465
	Trying fd80:10:1::15...
	telnet: connect to address fd80:10:1::15: Connection refused

on each/every mail submit -- via dovecot -- dovecot makes the connection

2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-server: conn 10.1.2.163:35388 [1]: Server accepted connection (fd=7)
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-server: conn 10.1.2.163:35388 [1]: Connection created
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 [1]: Connection created
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 [1]: Disconnected

looks up IP address

2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 [1]: Looking up IP address
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 [1]: Performing asynchronous DNS lookup
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-server: conn 10.1.2.163:35388 [1]: Sent: 235 2.7.0 Logged in.

finds BOTH IPs -- IPv4 & IPv6

2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 [1]: DNS lookup successful; got 2 IPs

then first tries to connect via the host's IPv6 address,

2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 [1]: Connecting to fd80:10:1::15:465
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 ([fd80:10:1::15]:465) [1]: Connecting
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 ([fd80:10:1::15]:465) [1]: Waiting for connect (fd=8) to finish for max 0 msecs

############ FAILS ############

2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 ([fd80:10:1::15]:465) [1]: Client connection failed (fd=8)

then proceeds to connect to the host's IPv4 address

2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 ([fd80:10:1::15]:465) [1]: Connecting to 10.1.1.15:465
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 (10.1.1.15:465) [1]: Connecting
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 (10.1.1.15:465) [1]: Waiting for connect (fd=11) to finish for max 0 msecs
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 (10.1.1.15:465) [1]: Client connected (fd=11)
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 (10.1.1.15:465) [1]: Connected to server (from 10.1.1.15:52880)
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 (10.1.1.15:465) [1]: Starting SSL handshake
2021-04-03 19:35:35 submission(mailer@mx.example.com)</tnO6xm/PIqsHgsH>: Debug: smtp-client: conn internal.mx.example.com:465 (10.1.1.15:465) [1]: SSL handshake successful
...

and submission continues/completes

I need to get Dovecot to stop trying/failing @ those IPv6 address submission connections.

Either by

(1) trying IPv4 *first*, before IPv6, to avoid the FAIL on submission

or

(2) turning off submission relay by IPv6 altogether, as I'll never use it

What's the config required to do either/both?