Brevo/Send-in-blue Emails are note being delivered

I recently integrated Brevo to send transactional emails. Using Zerocode’s plugin for it. Have just been using Sendinblue - Send SMTP Mail function.

It is working fine except, to some email ids the sent mails are not appearing in the inbox/spam/promotions/… The real-time statistics on Brevo’s dashboard show these emails as sent and delivered. But they are just not there in the recipient’s mailbox.

Anybody faced such issue and have you been able to solve it?