This is not a bug
The thing is that you installed AcyMailing locally and installation created update sites (Joomla feature using your localhost as the domain). Once you moved your site to the real domain, that update site is not updated automatically, because this is not something Joomla does
Remove AcyMailing entries in the Joomla Update sites and then manually install again AcyMailing installation package. That will create update sites with the correct domain and AcyMailing updates will work correctly in the future