Emails sent from contact form module to office365 accounts do not get delivered

[prestabee]

Using contact form v4.3 with prestashop v1.7
The module has been configured as follows

When the form is submitted, a copy of the email is successfully received by the Customer service and Webmaster email addresses.
If the sender's email is not from an office365 domain, the sender also receives a copy of the email. I have tested this with gmail.com, outlook.com, mail.com etc.

 

If the sender's email is from an office365 domain e.g. .ac.uk domains, a copy of the email is neither received in the inbox nor spam eventhough the backoffice email log shows that this has been sent. (The ones highlighted in red were never received)

 

When using the test email functionality, emails to office365 accounts are received successfully as shown below

 

 

 

 

 

 

Edited January 20, 2021 by prestabee (see edit history)

[prestabee]

Got some helpful comments on the github issue https://github.com/PrestaShop/PrestaShop/issues/22907