To update your Office 365 Password in PSA so PSA can send e-mails for you. Follow these steps
Log in to PSA
Click the yellow Email Inbox on the home page
Click the Settings button on the right side of the page
Then click on The Landings email account link
Use the Reset Password link next to POP3 Password and SMTP Password
Once you have changed the password, click the Save button at the top of the page.