Hi @michele mariotti ,
Welcome to our forum!
Agree with Michael Taylor, I tried to use machine translation to understand your problems, if there is any discrepancy with your expression, please forgive me! Please kindly understand that our forum only supports English at present, so we suggest to use English to describe the problem.
"Errore durante la preparazione dell'invio del messaggio di condivione".
For the error you provided, i have translated it and done research on it. I found a similar thread as yours, which mentioned some suggestions about how to resolve the issue (such as changing the permission, reinstalling office programs). Please check and try the suggestions in it:
Unable to send share calendar invitation invite within Outlook 2013
Hope to help you. If it doesn't work, please modify your issue to English and provide more information about your case.
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