Since you asked a philosophical question, I will respond with my philosophy on this issue.
- There are several problems with using the From address to sort such messages, including:
- Many organizations use more than one From address. They may even use more than one From domain.
- Anyone can spoof a From address. So a good phishing email might not get caught by the spam filter and would be filed into that special folder. It might be hard for you to determine if that message was really from your bank.
- So I use a special subdomain address at an alias I control when I sign up. You can nearly always change the existing address you signed up with to a new one. See: https://www.fastmail.com/help/receive/addressing.html
- You could use a single address for all such subscriptions, but if a spammer discovered that single address, you wouldn't know which organization leaked it.
- So I use a unique subdomain address for each subscription sign-up. For example, let's say you had control over the Fastmail alias "subs@example.org". if you signed up with a bank, newspaper, and gas utility you might use the addresses;
- bankname@subs.example.org
- newspaper@subs.example.org
- gas@subs.example.org
- If your Fastmail main account address was user@example.org, you could then set up the target of the "subs@example.org" Fastmail alias to point to a particular delivery folder. For example, you could point the alias "subs@example.org" to deliver to "user+subscriptions@example.org" if you had the folder "subscriptions" (case is ignored).
- If you wanted to set up a subfolder below "subscriptions" for each of the above examples, messages sent TO those subdomain addresses will be automatically filed as follows:
- X-Delivered-To: bankname@subs.example.org will result in X-Resolved-To: user+subs.bankname@example.org, which files the message into the subs.bankname folder (bankname subdirectory of subs).
- X-Delivered-To: newspaper@subs.example.org will result in X-Resolved-To: user+subs.newspaper@example.org, which files the message into the subs.newspaper folder (newspaper subdirectory of subs).
- X-Delivered-To: gas@subs.example.org will result in X-Resolved-To: user+subs.gas@example.org, which files the message into the subs.gas folder (gas subdirectory of subs).
- If you don't want to create the individual subfolders for each organization, you can still use those custom subdomain addresses and they will all file into the "sub" folder.
- The advantage of this method is that you don't have to use rules to file the messages. But rules can be used to override the alias folder target delivery folder.
I know that's not what you asked, but it's how I deal with a large number of these subscriptions without using any rules.
Bill