cannot send to ten or more recipients through outlook.com

I am setting up a user who wishes to advise all contacts of a change of email address to outlook.com.
Using emclient and a new outlook.com account, emails with a few recipients can be sent. A large number of recipients will not send, have reduced the number to ten and still will not send. How can this apparent anti-spam issue be overcome? The new account has been verified and security settings processed at outlook.com

I have hopefully solved the issue. Apparently when a new outlook.com account is established the limit on send email addresses is set about 10. The account has to be operated normally for several days to establish valid operations and then the limit is raised to 100.

Further testing indicates there is some a severe problem that I have not been able to solve  using the normal exchange settings for outlook.com. All previous installs have been Windows 10, this is Windows 7 64b !!!??? I cannot send to more than one recipient. see attached error detail. Driving me nuts.

Hello,
thank you for clarification on the outlook.com issue.

As for the second error - can you please copy the content of the Log tab (in the same window) next time the error pops up?

Regards,
Olivia

Amazing!!! the problem has gone this morning. I did re-install the LAN driver, and completely scanned computer with Kaspersky Internet Security. Neither indicated any problem. I suspect the problem was outlook.com server based security. Quite a  nasty time consuming experience.
Thanks for offering to help. Hopefully this is the end of the matter.