SSL certificate issue, server and smtp email delivery issue

I'm looking for a professional System Admin and server expert to look into ssl certificate and smtp issue on my project management platform which is resulting in failure for users added in a particular project with assigned tasks not receiving notifications prompts in their inbox.

Here is the error message received:

stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed

I will share with credentials in chat.

Please bid only if you are capable of doing the job.

Budget is 20 USD