The ping_threshold option is not a valid framework.mailer configuration key in Symfony Mailer.
This caused composer install to fail during cache:clear on deployment.
The option should be set as a DSN query parameter on the MAILER_DSN environment variable instead.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Set ping_threshold to 10 seconds so Symfony checks and reconnects stale
SMTP connections before reuse, fixing "451 4.4.2 Timeout waiting for
data from client" errors from Amazon SES.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>