Emails aren't getting sent

Description of issue or problem I’m having:
Hello everyone. We’ve been using Open Journal System for more than a year to run our journal. However, lately, we’ve been unable to contact reviewers using the platform because it is not sending any mails. I changed the registered contact mail in the server, thinking that it could be a problem from Microsoft, but it didn’t make any difference: the platform still not sending any e-mail, even when they tell me “Se ha asignado a Nacha para revisar este envío y se le ha enviado un correo electrónico de notificación.”
I noticed that the same is happening to Announcements. I could create a new one, but, then, I received a text like this:
There was a problem sending an email message. Please try again later, or contact your system administrator.”

I know this could be an easy issue, but I don’t have any knowledge about programming. Indeed, we have something similar to an administrator, but he is not familiar with the platform, so we need something similar to a tutorial to set up what could be causing us troubles.

I’m really grateful if someone could help us with this issue.

Application Version - e.g., OJS 3.1.2:

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

Hi @anamcardonavan,

As a starting point, you may wish to check out our administration guide section on emails: Email

Best regards,

PKP Team