You know...i'm trying to use it also and it just doesn't work.
I always get :"530 5.7.0 Must issue a STARTTLS command first. h43sm3407682wes.11".
I think this library is no good. I'm looking for another one.
I've never used as3maillib, but I access IMAP accounts via TLS using the as3crypto library that has classes to support TLS. Note however that the current TLS socket version of as3crypto does not work under iOS. I made it work under iOS, but it still needs alot of testing...
Not knowing as3maillib, I bet in combination with as3crypto it may give you a good start to develop email client functionality.