Why am I receiving exception from Office's Outlook library?

Question

I have an application that calls

Email hello = new Email(appropriate constructor);
hello.Email_Send();

I\'m receiving the exception:

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Answer 1

I ran into the same issue, and as previously said: if Visual Studio is running as Administrator then Outlook prevents another instance with a different user. My VS solution is starting several projects, and I need it to run as Administrator, so what I did is run Outlook as administrator while debugging. This solved my problem.