Office 365 – connection refused

Hi, hope someone can provide some help, or insight into this issue for me…

Trying to use WP-Mail-SMTP with Office365 and I’m getting the following error:

Error notice: stream_socket_client(): unable to connect to smtp.office365.com:587 (Connection refused)

My web host says:

“They have multiple IP’s bound to the hostname. Some of them are IPv6, which is not yet supported by our server. Bellow is my test that shows once it tried an older IPv4 IP address, it was able to connect.”

However I get exactly the same error when I try using the IPv4 IP address, even though my host says he can open a connection to that IP directly from the server.

Our email admin says he hasn’t come across the issue before, and Office365 suggested asking WordPress support.

My research found a few people who had this issue who discovered it was their host blocking certain ports on their firewall, my host assures me this is not the case.

Has anyone any pointers on how I might proceed to try to resolve this?