单项选择题 An email server has been installed； however， the staff reports that they are unable to receive email from external email addresses， but they can email each other.  Which of the following is the MOST likely reason for this？（）

单项选择题 Whichofthefollowingservertypesstoresusers’homedirectoryfolders？（）

单项选择题 WhichofthefollowingistheBESTwaytomakesurethenetworkprinterisautomaticallyinstalled whentheuserlogson？（）