Process mining aims at discovering different perspectives of business processes (BP) from event logs generated by BP management systems. However, BP can be entirely or partially performed outside such systems. Emails are widely used as an alternative tool to collaboratively perform BP tasks. Recently, there have been several initiatives to extend the scope of BP mining to consider email logs. However, most of them have been mainly focused on discovering BP activity perspective neglecting other equally important knowledge. Actor perspective is one of the important knowledge that can ensure more understanding regarding individuals acting for performing BP activities. Mining such perspective from emails logs provides additional information about the precise contribution of actors in the execution of BP activities. Such information is not limited to executing activities but also refers to requesting, informing, planning or observing activities' execution. This paper first formalizes the knowledge we may discover from emails related to actors perspectives. Then, it introduces an approach based on speech act detection from textual content of emails for discovering such knowledge. Our approach is validated using a public email dataset. Our results are publicly provided to be a first step towards ensuring reproductibility in the studied area.