Apparently, in both the "Messages" and the "SalesSigns" we suffer from the following problem - the emails are not synced properly with the email server: 

- New emails appear only after some significant time

- Emails there were moved from inbox to specific folders (labels in gmail) still appear and cause confusion

- Emails there were deleted still appear

- and more syncing issues... 

It looks like the IMAP was only partially implemented for these two features. Sometimes there are even discrepancies between the two features in that sense (for example - email that should appear in both, appear only in one of them, etc.)

The bottom line is that both features are not usable as we can not rely on them for incoming emails or at all. We must use a regular email client in parallel for that matter.  

Anyone knows why it behaves like that, and whether there is a solution to that? 

Thanks.