Fixes: #9613 Issue link: https://github.com/spring-projects/spring-integration/issues/9613 Sometimes even if `\Recent` or user flag is not supported by mail server, the `\Flagged` is also undesirable * Expose `AbstractMailReceiver.setFlaggedAsFallback()` to disable setting `\Flagged` on the message as fallback * As well as expose `MailInboundChannelAdapterSpec.flaggedAsFallback()` * Document the new option