Although I don't recommend pulling Office 365 business mail into a personal Gmail account, I know some users do this. For many, it just works, but others receive errors when they try to set Gmail up to use the Office 365 or Outlook.com SMTP server.
I have an Office365 Enterprise email account with a handful of users, one of whom has an aversion to anything Microsoft and wants to access his business email account using Gmail. He runs other businesses using Gmail and does not want to use Outlook. His solution is to set up his business Outlook email account as a POP account in his Gmail account. The problem? While we have no problem setting it up to POP mail from, the server, we can't configure Gmail to send using the Office 365 servers. It errors, usually with this message:
Authentication failed. Please check your username/password.
[Server response: Missed upload deadline (9.49s) (state SENT_SECOND_EHLO) code(0) ]
The username and password is correct. How do we make it work? I know we can quit at adding the POP account and he would receive the mail in his Gmail account but he wouldn't be able to send using the Office 365 account.
This issue hits some, but not all, users who try to connect to Outlook.com or Office 365 SMTP servers using Gmail. (Other services may be affected.)
If this happens to you, ping the server to find out which server the SMTP proxy is using for your account and use that in your Gmail settings.
Published March 23, 2016. Last updated on May 25, 2016.