My PortableApp TB Folder grow size

Hello! (Sorry, I write a unintelligible english. I hope everything to undestand).

Thank you can assistance me.

I have a problem to Portable Thunderbird. The folder grow in sizes. I purge a 'trash' 'Local Folder' but the size folder can not reduce size.

My USB memory size is 128MB of capacity, and I can not which a folder grow any more if conect for download e-mails.

Somebody help me. Thank you.

Javier.