> On 26 Jan 2016, at 15:56, Marc Schiffbauer <m...@sys4.de> wrote: > > * Sami Ketola schrieb am 23.01.16 um 23:27 Uhr: >> >> >> On 23/01/16 15:33, Robert Schetterer wrote: >>> for multiple advanced imap settings at migration you might use >>> imapsync not dsync Best Regards MfG Robert Schetterer >> Sure but imapsync does not preserve message UID's which means that users >> end up redownloading all their messages or message/UID mismatches will >> happen. > > IIRC that is not true. Some years ago I migrated a server to dovecot and > managed to do it with proper UID migration. No clients were required to > re-download Mail. Nor over IMAP neither POP3.
IMAP protocol doesn't have a way for clients to specify UIDs. Especially UIDVALIDITY can't be preserved in any way. IMAP clients don't necessarily make it clearly visible that they're redownloading mails though. With POP3 clients if they use the keep-mails-on-server it pretty much has to redownload mails as duplicates. Unless the UIDL was based on some email headers or such, the POP3 UIDL can't be preserved either.
