I just bumped into something silly that I know I’ll forget about in the future. Using the function in my PowerShell profile to open an Exchange Management shell, I ran the following command as part of a script.

try { Get-Recipient doesntexist } catch [Exception]{ write-line "No such mailbox" }

It’s a pretty self-explanatory command. I was trying to detect if a mailbox, in this case “doesntexist”, existed or not. Typically if the mailbox doesn’t exist, the Get-Recipient cmdlet will throw an error. My goal was to catch the error and do something productive with it but the above command doesn’t trigger the Catch block.

No problem, I thought to myself. My ErrorActionPreference is set to Continue by default so I’ll tweak it for this command.

try { Get-Recipient doesntexist -erroraction stop } catch [Exception]{ write-line "No such mailbox" }

The -ErrorAction Stop part should make the script stop executing on an error and hop into the Catch block. Wrong! The above command throws an error without triggering the Catch block, too.

It turns out I had to edit my $ErrorActionPreference variable to be Stop. Just using the flag in the command doesn’t work. I’ve run into this in other scripts where I import a PSSession, too. Now my command looks something like this.

Try { $OldErrorActionPref = $ErrorActionPreference; $ErrorActionPreference = "Stop"; Get-Recipient doesntexist } catch [Exception]{ write-host "No such mailbox" } $ErrorActionPreference = $OldErrorActionPref

First, I’m getting the current value of $ErrorActionPreference and storing it. Then I set the ErrorActionPreference to Stop. I run my Get-Recipient command which fails and now instead of getting an error, my Catch block is triggered. Afterwards, I set $ErrorActionPreference back to it’s previous value.

Now, because I’ve written a blog post about this, I’ll never forget again.