Postfix 2.6.2 has been released a few days ago and I installed and tested it on my test and production server and it all works as one should expect. There are no major changes in this release just some bugfixes which had not affected my systems.
The official release note for 2.6.2 is:
Postfix stable release 2.6.2 fixes one defect in SASL support. This does not affect Postfix versions 2.5 and earlier.
- With plaintext SMTP sessions AND smtpd_tls_auth_only=yes AND smtp_sasl_auth_enable=yes, the SMTP server logged warnings for reject_sender_login_mismatch, reject_authenticated_sender_login_mismatch, and reject_unauthenticated_sender_login_mismatch, instead of enforcing those restrictions.
For instructions on how to upgrade Postfix please read Upgrading Postfix.