The built in "Test outgoing mail configuration" yoursite/admin/settings.php?section=outgoingmailconfig is pretty accurate. If your SMTP provider contradicts that, you need a second opinion. For example, you could configure Thunderbird on your PC/Laptop and try sending e-mails using the credentials provided by your provider.
Thunderbird has the nice feature that you can leave some options as "Auto" and it tests many combinations for you. Once successful, find out the specific settings one-by-one and compare with what you've been doing.
Any serious SMTP provider will debug with you. They look at the log trace at their end and tell you what you've been doing wrong. (They don't have to debug the Moodle side, as they claim, they need to look at what happens on their side.)
BTW, the port 485 is already suspicious, port 587 is more common.