Arrgh… Error: Exception: Invalid API key (in vendor/mandrill/mandrill/src/Mandrill.php line 153)

#0 vendor/mandrill/mandrill/src/Mandrill.php (132): Mandrill->castError(Array)
#1 vendor/mandrill/mandrill/src/Mandrill/Messages.php (80): Mandrill->call('messages/send', '{"message":{"to...')
#2 admin/classes/Mail/Providers/MandrillMailProvider.php (45): Mandrill_Messages->send(Object(stdClass))
#3 admin/classes/Mail/Mail.php (123): Exsited\Mail\Providers\MandrillMailProvider->sendMail(Object(Exsited\Mail\Mail))
#4 site/templates/mailing.php (103): Exsited\Mail\Mail->send()
#5 wire/core/TemplateFile.php (287): require('/data/sites/web...')
#6 wire/core/Wire.php (380): TemplateFile->___render()
#7 /data/sites/web/bellisroes

This error message was shown because: site is in debug mode. ($config->debug = true; => site/config.php). Error has been logged.