Hi @Andrea Vironda ,
According to your description, sync issues about your Outlook contacts seems only happened to your Outlook for Android App, right? If so, please check your Outlook for Android app version and make sure you have upgraded your Outlook App to the latest version.
As I know, if you set up your email as an IMAP or POP account, your calendars and contacts won't sync. You'll have to add them as an Exchange ActiveSync account. Also please check and make sure that your email app has the correct permissions to access your contacts. Here is some troubleshooting suggestions for contacts sync issue: Can't sync calendar and contacts with my phone or tablet.
If the issue still continues, you could also try to completely uninstall and reinstall your Outlook for Android app, re-add your email account to see if the issue could be resolved. Notice: Before, operations, please make sure you have backed up all your data.
By the way, please kindly understand that here we mainly focus on general issues about Outlook desktop client and know little about Outlook for mobile. If all those suggestions could not help, it is suggested to post a new thread to the dedicated forum for Outlook for Android.
The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thanks for your understanding and hope your question will be resolved soon.
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.