Output Based on Email Address with Env Variables

How to get output with Env Varaibles

if(
    contains(outputs('Export_Email_Alias')?['body'], parameters('Mailbox1 (st_Mailbox1)')), 
    parameters('Mailbox1 (st_Mailbox1)'),
    if(
        contains(outputs('Export_Email_Alias')?['body'], parameters('Mailbox2 (st_Mailbox2)')), 
        parameters('Mailbox2 (st_Mailbox2)'),
        if(
            contains(outputs('Export_Email_Alias')?['body'], parameters('Mailbox3 (st_Mailbox3)')), 
            parameters('Mailbox3 (st_Mailbox3)'),
            if(
                contains(outputs('Export_Email_Alias')?['body'], parameters('Mailbox4 (st_Mailbox4)')), 
                parameters('Mailbox4 (st_Mailbox4)'),
                if(
                    contains(outputs('Export_Email_Alias')?['body'], parameters('Mailbox5 (st_Mailbox5)')), 
                    parameters('Mailbox5 (st_Mailbox5)')
                )
            )
        )
    )
)