1. If you are using Oracle listener with SID for connection string then check if oracle client installed on worker trying to lookup TNSNAMES.ORA usually at Windows path <Oracle Client Path>\Network\Admin
2. Strange that it worked in UAT, but only change may be Ignio capability version/config or client Prod SMTP relay. Please check if you’re using special characters other than @ in the sender email address. May need to enable UTF-8 encoding at Sendmail configuration side.