[bsnnkv]

My semi-related suggestion: Even if you don't use it now, download Thunderbird (you can delete it after), add your Gmail account, then once it has synced, select all the messages you want (maybe even your entire inbox for good measure), then go to File -> Save As -> File. The folder you select here will be populated with your emails as EML files.

Once you have that folder, just use unsubscan to get all the links presented to you in a static HTML page broken down by sender domain.