@Varun-Ganesh-D After updating what? Do not know jack about SES but seems whacked to me that updating only NodeBB would result in such. Perchance might some other, more system wide updates also been in the lurking?

Presuming you have cli access, what returns when thou drivest the following:

[root@forums ~]# which sendmail
/usr/sbin/sendmail

Should be similar to above, and, of course, be in your $PATH.

Rock on!