[MlMt] Updating account information made MailMate (re)download *all* email

[Adam Liter]

>> Now, it looks like this should be ok with FastMail, but then it seems 
>> something else happened. The redownloading of emails indicate that 
>> the `UIDVALIDITY` value changed of each mailbox. Each email is 
>> uniquely identified using the `UIDVALIDITY` of the mailbox and the 
>> `UID` of the message. If the `UIDVALIDITY` value of a mailbox changes 
>> then MailMate MUST delete its local cache of emails and then fetch 
>> the “new” messages of the mailbox. There is no way to tell 
>> MailMate to ignore `UIDVALIDITY` changes.
>>
>> Hmm, MailMate should also warn you when the latter happens which 
>> makes me think that this might be a MailMate bug after all. I have a 
>> FastMail test account and I'll note to test what happens when I do as 
>> you describe. Sorry about the inconvenience if this turns out to be a 
>> bug.
>>
>
> I did not see any other warnings besides that first one.

For what it's worth (probably not much), this just happened to me with 
iOS Mail. I updated to iOS 10 last night. So perhaps it is more of a 
FastMail problem, rather than a MailMate problem? Note that I haven't 
set up 2FA with FastMail, however. So I'm not really sure how 
helpful/relevant this anecdote is.

-Adam