You would need to enable Database email extended procedure using Database Mail XPs configuration option:
EXEC sp_configure 'show advanced options', 1;
GO -
RECONFIGURE;
GO -
EXEC sp_configure 'Database Mail XPs', 1;
GO -
RECONFIGURE -
GO -
Now you can test the configuration by sending emails using sp_send and sp_notify_operator procedures.
Reference:
https://techcommunity.microsoft.com/t5/azure-sql-blog/sending-emails-in-azure-sql-managed- instance/ba-p/386235