If we're getting into reasons, let me explain mine...
I was trying to decide how to get rid of
disposable (temporary, short lifetime) email addresses where more than one is using the
same alias.
For example, say the alias is
disp@fastmail.com, then I can have any number of temporary (disposable) email addresses using that alias with subdomain addressing. For example,
x@disp.fastmail.com,
y@disp.fastmail.com,
z@disp.fastmail.com, etc. They would all be sorted into folders x, y, and z if those folders exist. Or they could be grouped as subfolders under some outer folder if
disp@fastmail.com's "Deliver to" is set appropriately.
The lifetimes of these aliases are different so some I want to keep longer than others. So what to do with the ones I no longer need? I cannot delete or disable the actual alias (
disp@fastmail.com in the example) since that would take them all out. I've been thinking of sending the messages to the ones I want to remove to the trash
as unread just so they stand out a little more. Alternative solutions would be filter into a new single folder designed for this purpose or send them to spam. In all cases as unread to make them stand out a little.
This is only for that kind of alias. Unique aliases for more permanent registrations, etc. can simply be disabled or deleted if I want them to cause a bounce. Other choices are to keep them "alive" but issue a reject to ones I no longer want or like the disposables send them to a folder (trash, spam, or special folder for this purpose).
I'm doing this all with sieve code since I prefer
not to write individual UI filters for each alias whose life has expired (plus I don't believe I could use the UI anyway for the disposables). I think it's simpler and "reads" better just to list the email addresses in, well, a sieve list.
It's a work in progress so I haven't decided yet (opinions welcome). But I currently have the disposables going to the trash as unread. That's what prompted me to start this thread (and I've since submitted a ticket to see what FM says too).
Note, in reality I don't have any aliases to add to these lists as yet. I'm only adding the code as a place holder for the day I will need it. It's all this spare time I have on my hands due to this damn virus keeping everyone mostly at home!
