From the OP: 

my $smtp = Net::SMTPS->new( $server, Port => $server_port, Debug => 1,
+ doSSL => 
+$mail_sasl_type) || die "cannot connect to server ${server}";
my $sasl = Authen::SASL->new( mechanism => 'PLAIN', debug => 1, callba
+ck => {pas
+s => $pass, user => $user}); 
$smtp->auth( $sasl ) || die "cannot do mail auth";

[download]

From the output you posted I see the die statement is where it fails at $smtp->auth( $sasl ) || die [...]. Looking at the auth() method I found the documentation points out a difference in Net::SMTPS and Net::SMTP. You might try to specify the AUTHMETHOD as shown at Net::SMTPS.

METHODS

Most of all methods of Net::SMTP are inherited as is, except auth().
auth ( USERNAME, PASSWORD [, AUTHMETHOD])
Attempt SASL authentication through Authen::SASL module. AUTHMETHOD is
+ your required method of authentication, like 'CRAM-MD5', 'LOGIN', ..
+. etc. If your selection does not match the server-offerred AUTH mech
+anism, authentication negotiation may fail.

[download]

Also, the synopsis for Authen::SASL shows mechanism specified as a list of the choices. You only provide PLAIN but it might be looking for one of the other options shown in your debug output.

SYNOPSIS
use Authen::SASL;
 
$sasl = Authen::SASL->new(
  mechanism => 'CRAM-MD5 PLAIN ANONYMOUS',
  callback => {
    pass => \&fetch_password,
    user => $user,
  }
);

[download]

Debug output from Net::SMTPS :

Net::SMTPS=GLOB(0x562fb253e128)<<< 250-AUTH PLAIN LOGIN CRAM-MD5 DIGES
+T-MD5

[download]

In reply to Re: Net::SMTPS => auth no longer works - Migration from Debian to Docker container by Lotus1
in thread Net::SMTPS => auth no longer works - Migration from Debian to Docker container by initB10r

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