wordpress is not sending emails

Hello, im using wordpress multisite and i set my following email settings from Network > sites >setting

Mailserver Url Mailserver Login Mailserver Pass Mailserver Port

but unfortunately no mails are going. same details are working for another php application hosted on same server in another sub-domain. only difference is on that php application, i could setup authentication on, here no such option…

so i install check mail plugin to find out the cause of the issue, and on check-mail plugin, i can see my current email setting are as following.

Current mail settings

SendMail path (UNIX): /usr/sbin/sendmail -t -i SMTP server (Windows): localhost SMTP port (Windows): 25 Add X header: 1

now i cant understand why & from where this is coming. anyone can guide me to resolve this?

thanks