#### 3.7.3 Synchronizatiom Mode ¶

When given the `--preserve` option, `movemail` retains already downloaded messages in the source inbox. This means that called second time it will download both recently delivered messages and the ones it has already downloaded in the previous run. This makes little sense and a special option is provided to avoid this.

The `--sync=mode` defines synchronization mode, i.e. the algorithm that helps `movemail` decide whether a particular message has already been downloaded or not. If it has, `movemail` will skip that message.

The mode argument can be one of the following:

`all`

  Assume each message is new. This is what `movemail` does when called without the `--sync` option.

`uidnext`
`imap`

  Use the combination of uidvalidity and uidnext parameters of the source mailbox. This mode is mostly useful when the source is a remote mailbox accessed via IMAP4 protocol.

  When using this method, `movemail` stores additional meta-information about each ‘`source-destination`’ pair of mailboxes in directory `.movemail.sync`, in the user’s home directory. The location of that directory can be changed using the `--sync-dir` option.

  Example usage:

      movemail --preserve --sync=uidnext imap://server mbox

`uidl`

  Use `uidl` message identifiers. This method is useful if the source is a remote mailbox accessed via POP3 protocol.