Error occurring in sending mail for Forget password

I have set up laravel 5.6 on server. When I try to use Forget Password, I am gettting error after enter email id:

Class Swift_AddressEncoder_IdnAddressEncoder does not exist

actually, it was working find two days before but now i dont know what happen...I have done thing in it.

below connection in .env:

 MAIL_DRIVER=smtp
    MAIL_HOST=smtp.sendgrid.net
    MAIL_PORT=587
    MAIL_USERNAME=apikey
    MAIL_PASSWORD=SG.EcuUbtbhSbq1IAh**1tPQg.uFah8Jw**7lh10wGpA_CPU01ySmAC26HFylz_BFI
    MAIL_ENCRYPTION=tls
    MAIL_FROM_NAME="Your Trade Log"
    MAIL_FROM_ADDRESS=support@y**r**r*a**.com

this is live link for Reset Password: YourTradeLog

via Chebli Mohamed