Steps to reproduce the issue

Upgrade to 3.9.23

Expected result

SMTP function works correctly

Actual result

Could not start mail function.

System information (as much as possible)

Setting Value

PHP Built On Linux web2 4.19.0-12-amd64 #1 SMP Debian 4.19.152-1 (2020-10-18) x86_64
Database Type mysql
Database Version 5.5.5-10.3.25-MariaDB-0+deb10u1
Database Collation utf8mb4_general_ci
Database Connection Collation utf8mb4_general_ci
PHP Version 7.3.19-1~deb10u1
Web Server Apache/2.4.38 (Debian)
WebServer to PHP Interface fpm-fcgi
Joomla! Version Joomla! 3.9.22 Stable [ Amani ] 6-October-2020 15:00 GMT
Joomla! Platform Version Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT
User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0

Additional comments

After update from Joomla! 3.9.22 Stable to 3.9.23 the SMTP auth stopped working. When sending test email with the following settings:
SMTP server smtp.sendgrid.net
SMTP port 25
TLS authentication

Direct downgrade to v. 3.9.22 fixed the problem.
I suppose that the new way displaying the password breaks the feature.
We use the system email account with external mass email plugin to send newsletter. The plugin also stopped working.