Gmail Question

Looks like the OP got his answer? I also use Thunderbird at home, mainly due to having multiple free email accounts from different services. Though the one advantage of creating a rule in webmail is that it works for every method you use to retrieve your mail, such as in a client or mobile email app. If created in Thunderbird, it only works in the client.

Though Thunderbird has an advantage of saving a copy of email locally(offline). And not have to sign-in online to read old email.