Diagnostics:
./launcher enter appopenssl s_client -connect smtp.beget.com:465 -servername smtp.beget.co
Test in Rails:
./launcher enter app
rails c
ActionMailer::Base.smtp_settings = {
  address: 'smtp.beget.com',
  port: 465,
  user_name: 'admin@email.com',
  password: 'password',
  authentication: :login,
  ssl: true,
  tls: true,
  enable_starttls_auto: false,
  openssl_verify_mode: 'none'
}
# Тестовая отправка
ActionMailer::Base.mail(
  from: 'admin@email.com',
  to: 'admin@email.com',
  subject: 'Test from Rails',
  body: 'Test message'
).deliver_now
This results in a clear error text