Its' not what I asked here: https://www.wilderssecurity.com/threads/gmail-delete-only-the-attachments-from-the-emails.386906/, but this program can be useful for someone: http://gearmage.com/maildownloader.html; I tried it and it works.
seems useless as free version, only one account - manual switch to another account aso. and the pro "limited" is a full joke with only 3 accounts. and pro full is really expensive unfortunately there is no much choice http://www.c2s.co.uk/mail-attachment-downloader/ https://sourceforge.net/projects/emailattachment/ went commercial -> http://www.websoftware.co.nz/attachment-grabber/
