BalaReva is a custom activity package. Any reason you are not using the UiPath Mail activities?
Regarding what you are doing, hard to answer unless we see your full expression but it says you are missing arguments, I think you’d like need to use Invoke Method rather than Write Line long term of course.
I have tried using UiPath Mail Activities the Send Outlook Mail Message Activity works fine but Get outlook mail message gives the below error
System.Exception: Job stopped with an unexpected exit code: 0xC0000005
I tried a few solutions offered on forum but could not resolve it so I was able to get mail messages using balareva activities certain mail messages have image in the body and I want read that image hence I am trying to save the mail