We still have this issue with TDM Portal version 4.9.321
When we export masking configuration from the portal, we see epassword property in connection file generated even if the username is in the form of : ext:<plugin>:<alias>.
Release : 4.9.1
Component : CA Test Data Manager - Others
The fixed binaries are TDMWeb-4.9.333.0.zip and FastDataMasker-4.9.174.0.zip
Available from: TDM Support Patches