IMAP Gateway: Supply UID in APPEND

[Andreas Hügel]

the APPEND command should fill in the UID directly when generating the email. This requires the separation been prepared for by introducing the FolderHelper.

Reason:
Loading many mails into the Mailbox will lead to a long processing of the sequence list. That is, because at that time the UIDs need to be stored into each email, if it is missing.

Warning:
changing this will destroy the existing functionality for the \Recent flag. Decision needs to be made on how to handle that. Using a property will lead to further changes to the email store at the time of sequence list processing. But that amount will be less than creating UIDs.

[Andreas Hügel (andreas-huegel)]

Adding UID has been added to APPEND and COPY

the concern regarding \Recent flag is not valid. \Recent flag is to highlight emails which have been received, not emails which have been added to the store by the user himself.