Update after some experimentation. Initial tests did confirm saved post/mail can indeed by wiped after a Town Import into Welcome Amiibo, though my final transfer of my own main New Leaf did to my surprise retain the save mail in the Post Office. I remain confused as to why the mail can (but not always) be lost on Town Import, but can at least detail my findings should anyone else find this post with the same questions I had.
I first tested a spare copy of New Leaf on a fresh save file (New Leaf and Welcome Amiibo games updated to the latest versions as of Oct/Nov 2021).
I started a new town, progressed very little just so I could save mail in the post office.
Transferred to Welcome Amiibo, and my post office mail boxes were empty. Post was lost, as also reported in that old reddit post. They mentioned a few different things, but I believe the "Town Import" of Welcome Amiibo is indeed the culprit of mail getting deleted.
I wiped the Welcome Amiibo cartridge save (A+B+X+Y held from 3DS menu as the game loads), then I prepared to transfer my main New Leaf save after keeping my favourite 10 mail on hand, assuming the rest would all be deleted.
To my surprise, my save retained all the mail on the Welcome Amiibo cartridge! I have no idea why. I can at least note it is possible for mail to survive the transfer, though it is worryingly inconsistent. I can only detail the mail status of my save, presumably some part of which was different enough to stop the mail from disappearing.
Unfortunately, I have no guarantee that any of the below will be enough to stop the mail being deleted. These are just my best guesses as to likely responsible differences in my main New Leaf save.
- New Leaf save file was several years old
- Only one player in the town
- All post office mail storage boxes full (Approx. 40% of mail had attached items)
- My house post box was not overflowing. There were 4 mail not yet transferred out of the house mailbox.
Other than my guesses above, I'm afraid I've no idea why sometimes mail is indeed deleted but not always. Perhaps I just got lucky!
I can also confirm that Town Import did indeed save everything else I could think to test in my town, EXCEPT for the Happy Home Showcase.
My transfer was from a digital New Leaf save, to a cartridge Welcome Amiibo.
All rooms in my house, storage, extra storage house extension, 2nd floor museum exhibits, custom designs, stored money in post office, current items on display for purchase in Re-Tail, etc. Everything bar the showcase which is now empty transferred safely (goodbye Nintendo Pikmin house). I even got a badge from the badge man since the transfer to the Welcome Amiibo cartridge, so all the other details of my player and town appear to be safe.
Hope this info may help others.
