Increase email log size

Hello Guys,
A great plugin indeed. Works very well. Recently i needed to get access to the email log for a customer who purchased from me about 2 weeks ago. Sadly i discovered that the log of the plugin goes back only about a week or less. Perhaps it can be number limited.

My question to you is – how can i increase this log? I need it as big as possible. I have plenty of space on the server?

As im using a simple SMTP service for the Post service – there are no logs there at the provider.

Thanks in advance