Strange Garbage Characters

Since last few days I am observing a strange issue. When I try to import the email list Mailwizz reads the @ symbol as +AEA- and gives an error that this is not a valid email address. Today I also observed that it converted underscore (_) symbol to +AF8- and thus even changes the column name from DATE_ADDED to DATE+AF8-ADDED. Has any one seen this issue and any clues how to fix it ?