Laravel Mail Queue Issue

Currently, I am implementing the mail queue for my web application. The mail information gets inserted into the jobs table and dispatched. However after dispatched, I checked the failed_jobs table and below is what I currently retrieved from the table: SSL operation failed with code 1. OpenSSL Error messages: SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed' in [login to view URL] I am using Exim. My laravel environment (.env) file settings are as below: #MAIL_DRIVER=smtp #MAIL_HOST=localhost #MAIL_PORT=25 #MAIL_USERNAME=null #MAIL_PASSWORD=null #MAIL_ENCRYPTION=null I have attempted to verify my openssl by issuing the following command: openssl s_client -host localhost -port 25 -starttls smtp The result generated by the above command is verify return code: 21 (unable to verify the first certificate). I checked my configuration and it looks fine. Also I attempted to modify the laravel mail configuration by inserting stream code but that also failed. before any of the error above generated, I had a problem with mail queue. I was receiving the following error: Messages from my IP address is temporarily deferred due to user complaints. After that i'm receiving the ssl error. The deferred issue only occurred when sending mail to yahoo. I tried sending mail to gmail and hotmail, first day it worked. However, the next day, when I tried it failed. The SSL error is generated. You must complete this task via remote desktop.