First, I advice you to upgrade Mapilab POP3 to the latest version
(v.2.6.0.) It will not solve current problem but it will help you to get technical support faster. Regarding the problem -- look at the Mapilab Connector service properties at the Dependencies tab, this service requires other service to be started (microsoft exchange transport) so if this service doesn't start at first time -- Mapilab POP3 Connector service will not be started too. Microsoft Exchange Transport can be started in second or third try but Mapilab service will not be started.
To solve the problem with starting Mapilab POP3 service it is necessary to solve the problem with starting of Microsoft Exchange Transport.