Jenkins E-Mail Notification don't Work

I am working on sending mail after the build result.
23 people were designated as Recipients to send the mail, and it was successfully sent to the mail server.
However, there are cases where the mail is not received, only a few people receive the mail, or it arrives in 10 minutes.
Is there any way to solve it?

If the mail is delivered to the mail server, then you will need to talk to your IT department to figure out why the emails are not being sent. At that point it is outside the Jenkins area and into your IT infra