Almost every single airline, hotel, car rental, and other travel-related company that remotely interests me has my e-mail address for their mailing list. 99% of the time, I don't bother to read their e-mails. After about a month, I will have 800-1000 unread e-mails piled in my inbox.

I wonder if there is a Thunderbird add-on that can do the following..

* Every month, scan my inbox for keywords (whether it's subject or e-mail) of my choosing.
* Depending on the keyword and if the e-mail is more than x days old, it will automatically delete it. For example, weekly deals from an airline can be deleted if not read within 7 days, but mileage statement e-mails from that airline can stay for 14 days.

Tried searching but had no success.