Office 365 outlook will not send message to gmail accounts but receive

Since updating to Windows 10 my Office 365 Outlook will not send emails - error unable to connect to network - yet it receives them OK and if I go to account settings and use 'Test' it sends and receives OK this is true of all my accounts, Hotmail, gmail and two domain accounts. All can be set up and work from the new Mail App. Have run online repair of Office 365 and rebooted to no avail, anyone any ideas

This is the exact problem from another's old post. The resolution of SFC / scannow did not show any errors on my computer. It is a new build and the day I added email accounts everything worked and the next I could receive but when I try to send it errors with a 0x800ccc0f code.

Bro67 - Both the Gmail side and the outlook side are correct, I even tried changing the send port to 25 with no SSL and that did not work, I have two other windows 10 computers that work with that account and the difference is this one has Office 365 and the others are 2016 Professional Plus.

Bro67- I am a network engineer and fully understand ports and protocols and tried all the listed settings. This is not a mis-configuration

I have the exact same problem. Brand new computer. OS loaded Dec. 13 by Dell. Worked great until it didn't. Suddenly same problem exactly as described above.
After a week of struggling I am positive is not a gmail or google account issue. The same problem applies to all my accounts - multiple POP and MIME accounts so both PST and OST files involved. I have created a new profile, run the Microsoft PST repair tool on the data files, reloaded Outlook, tries multiple ports and protocols (always leaving one unchanged for a control) and some other stuff I have forgotten already. Nothing does any good.
I may try switching one of the accounts to a new data file but if the issue was file related why ALL of them? I have 7 accounts (don't ask).
Anyone else? Any ideas? I do NOT want refresh the OS. Have never done it before and know I would screw it up.
Thank you just for reading this.

GOT IT!! Kill the smartbyte task. Stop the smartbyte service. Expunge Smartbyte from your system altogether (via Apps and Features - two components to uninstall). Voila - Outlook will send mail!
I found this by accident looking through all the running processes out of curiosity. Smartbyte had caused a network speed problem in my last system so I killed it. Suddenly mail was working. That is twice Dell has bitten me with the same rotten piece of software.
Hope this helps others. Drop a note if you need help or this doesn't solve the problem for you.
I am so relieved.

Hi Wiiiindy, just registered on this forum to say thanks.
I had the same issue on a new Dell Inspiron with Office365 and your suggestion to kill Smartbyte sorted it. Don't know how Dell can package software that causes such problems, but thanks for the info - Outlook works fine with Smartbyte removed.

Any other ideas how to resolve issue.

I keep getting

Your message did not reach some or all of the intended recipients.

Subject: test
Sent: 09 08 2022 06:20

The following recipient(s) cannot be reached:

xxxxxxxxxxx@hotmail.com on 09 08 2022 06:20
None of your email accounts could send to this recipient.