[jdmc]

Originally Posted by noclue

I have three FastMail addresses ending in fm, us, and net. The "US' is my commercial account. The "net' is the newsletter account. The fm (com) is my personal email account. The newsletters end up in any of the three accounts.

Being very careful with nomenclature is important in cases like this to avoid misunderstandings. I suspect that you're using the term "account" here to mean something different from the word's strict definition in the context of a technical discussion about email. Rather, I suspect that you have exactly one FastMail account; that the canonical email address associated with that account (i.e., the address you would type in as your username when freshly logging into the Web interface) is the one ending in "@fastmail.fm"; and that you've created two alias email addresses that are associated with that same account, one ending in "@fastmail.net" and the other ending in "@fastmail.us". Is that correct?

Meanwhile, inside your FastMail account, there exists a set of mail folders, which may or may not be nested hierarchically (i.e. with sub-folders "inside" a parent folder). In the context of this discussion, the terms "account" and "folder" mean very different things. For clarity, let's try to be consistent in using each of those terms according to its precise meaning.

Originally Posted by noclue

Each morning I move the newsletters to their corresponding "net" folder from the "fm" and "us" folders and from spam.

Okay, this is an important aspect of troubleshooting your situation: Please post a list of all the folders (and sub-folders, if any are nested) that presently exist within your FastMail account, as those folders appear in the column down the left side of your screen when you're viewing your account in the Web interface. (Or if you know how to take a screenshot image, you can post a screenshot of that folder list instead.) If you have any "parent" folders that contain sub-folders, please be sure to show all the sub-folders indented directly underneath their parent folder.

Originally Posted by noclue

So my assumption is that FastMail isn't learning like it did in the days of old.

I've been a FastMail user for something like 16 years, and as far as I know, FastMail has never had a feature whereby it "learns" where certain messages are supposed to be filed in your folder hierarchy based solely on "watching" as you move messages from place to place by hand. If I'm right that such a feature does not exist in FastMail and never has, then any automatic placement of incoming emails into certain folders other than your main "Inbox" folder that you may have observed in the past was being driven by some other process, such as the one that does so if the destination address of an incoming message is formatted in certain special ways that make reference by name to the folder into which it is to be delivered.

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By the way, in my previous post from last night, there are many specific questions that I asked to which you did not respond. It will help me to help you if you would kindly answer all those questions, please.