How to set up Outlock mail on the Bitrix virtual machine?

Question

1C-Bitrix

Good afternoon.
vmbitrix 7.5.0
is used We use Microsoft Outlook, all letters coming from @mysite.ru get into Outlook and are distributed among departments.
When using the hosting server smtp - letters reach @gmail.com, but do not arrive at @mysite.ru and do not get to the outlook client. Hosting technical support recommended in this case to use the Outlook smtp server (smtp.office365.com). In this case, letters stopped coming at all, error code:

smtpmsg='451 4.7.0 Temporary server error. Please try again later. PRX4 [PR1PR01CA0024.eurprd01.prod.exchangelabs.com]' errormsg='authentication failed (method LOGIN)' exitcode=EX_NOPERM

Now the hosting says that the problem is in Outlook, and the Outlook admin says that the problem is in the hosting.

.msmtprc config
account mysite.ru
logfile /home/bitrix/msmtp_mysite.ru.log
host smtp.office365.com
port 587
from [email protected]
aliases /etc/aliases
keepbcc off
auth on
user [email protected]
password password

tls on
tls_certcheck off

Help with Outlook email settings

Answer 1

The problem was solved by installing and configuring Postfix

Answer 2

And what was in the logs in the first case when the sending went through the hoster's smtp?
Since there letters reached gmail, it means that everything was relatively normal.