OJS Stops to send email and notifications

Dear PKP Team,
OJS Stops to send notifications and email please help me out as I resolve the issue.

Hi @ahsan551,

Can you please provide more details - such as:

Description of issue or problem I’m having:

Steps I took leading up to the issue:

What I tried to resolve the issue:

Application Version - e.g., OJS 3.1.2:

Additional information, such as screenshots and error log messages if applicable: