Quoting original submitter:
,-------
| Please don't disable interface elements when not really needed, for                          
| example:                                                                                     
|                                                                                             
|  * Configuration menu is disabled when the mail check is in progress.                        
|  * Preferences windows are modal and make it impossible to continue                          
|    writing or reading mails.                                                                 
|  * Can't reproduce it now, but opening Compose window used to block                          
|    certain menu items.                                                                       
|                                                                                             
| As I understand, this is done to ensure that mail check process (and                         
| other things) use consistent settings; however, it's probably better for                     
| them to just acquire a copy of the settings when they start, so user can                     
| safely change anything without affecting running processes.
`-------