Email set up....

Hello all... have a question and maybe someone can help me with it.    Our sitelink email runs thru our gmail account.... due to suspicious activity elsewhere I had to change our email password on gmail account...then changed it on sitelink email set up page..... but when sending emails from sitelink to tenants they always shoot back as failed.   ANyone know what I am doing wrong?  I appreciate any help you have... as of now tenants are not able to receive receipts or invoices from sitelink software.

Thanks