OpenSSL::SSL::SSLError after rails 6.0 with ruby 2.7 -> to rails 6.1 with ruby 3.0

Question

I have updated my rails 6.0.4 app to 6.1.3.2 and ruby from 2.7.3 to 3.0.1

On sending a test email in development I get an error:

OpenSSL::SSL::SSLError
hostname "mail.ABCD.com" does not match the server certificate

I have not changed my configuration, it was - and is

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
 address: Rails.application.credentials.smtp[:server],
 port: Rails.application.credentials.smtp[:port],
 user_name: Rails.application.credentials.smtp[:username],
 password: Rails.application.credentials.smtp[:password],
 authentication: :login,
 enable_starttls_auto: false
}

I have tried to add

openssl_verify_mode: 'none'

It made no difference. This is happening from localhost:3000 - I have not yet deployed the updated app, and obviously, I did not have this issue before updating...

Edit: I have moved the rails 6.1 app to ruby 2.7.3 and the emails send from localhost:3000 without problem. So it must be ruby 3.0.1. Thanks for helping!