PHPMailer connection error after WP-local export to go live

Hi everyone,
Hope someone here can help me with this…

I built a website locally using local-wp, and then used the wp local wordpress plugin to go live.
Everything went smoothly. Except one MAJOR issue:

Wordpress cannot send emails (system and contact forms etc…).
I tried to use smtp plugins (multiple ones): no success. I constantly get the following error:
SMTP ERROR: Failed to connect to server: Connection refused (111)SMTP connect() failed.

My SMTP settings are right and my domain host (OVH) and mail server (Exchange) are well-configured, and working well outside of this issue with Wordpress.

Also, my admin email is still " dev-email@flywheel.local ", and impossible to reset it via the wordpress interface as it requires to validate the new adress and WP cannot send any mail. I used a plugin to go over this verification and succeeded to change it. BUT, when setting up any plugin (WP SMTP for example) it keeps displaying " dev-email@flywheel.local " as if it was the default admin email and nothing has changed in the backend and the change is only on the frontend (when I check Dashboard → Settings → General it displays the right email).

My guess is that these 2 problems are corelated. But I cannot find anyhow to fix this…
Is there a way to correct this ? via ftp ?

I can provide more input on my installation, settings ect… if needed.

Thanks in advance !