Facing issue while sending/fetching mail using office 365 in an application

Hello,

We are facing a very strange issue while sending/fetching mail using office 365 mail on account getting this error "

"""
Failed to authenticate on SMTP server with username "nitinkaushik2016@outlook.com" using 1 possible authenticators. Authenticator LOGIN returned Expected response code 235 but got code "535", with message "535 5.7.3 Authentication unsuccessful [BL0PR0102CA0044.prod.exchangelabs.com]

"

any leads would be appreciated.