Re: Are you the K that was the instigator of the nine?
Um, no idea but - I have nothing to do with Nine Email App for Android.
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Regarding migration - yes it should be possible to migrate to another email service / server, and have it collect mail from the AOL account catching up every few minutes.
Maybe there is even a way to have AOL / Yahoo do this from their side.
And then in Aqua Mail it should be possible to add the old address as an alias / identity and use it for sending.
Should be doable.
One thing to keep in mind is - if you migrate, messages can be stored in the new server "out of order" (i.e. not by date received).
If this happens and Aqua Mail starts showing you very old messages, please see the FAQ
https://www.aqua-mail.com/search/?q=datesunder
"Messages out of order, or wrong message dates"