The screen of the menu Options\Preferences lets you set the options for the Synchronization of MesNews :

ZoneSynchronization:

This part is used to set the frequency you want the groups to be checked.

Refresh of the selected group (minutes) : this is the frequency , in minutes, to check the "subscribed" group. The value of 1 (default) means that MesNews will check the group every minute to see if there are new messages, and will download them automatically.
Synchronization frequency (in minutes) : shows, in minutes, the download frequency of the groups for which a Synchronization method was set.
Activated Synchronization: when unchecked the groups will not be synchronized. You can disable the sync temp via menu Options Synchronize of the other groups.

Zone Load bodies of messages (synchro) :

Here you can set the method of Synchronization to be used when you are leaving a group and when not all messages are loaded yet, according to choice made in Synchronization of a group.

Group not synchronized : when ticked and you leave a group, that has no sync method set, while messages are loaded, the the group will be memorized, at next visit to the group the downloading of the messages will be restarted.
Group is synchronized (amount new messages) : when ticked and you leave the group, that has a sync method set as "amount new messages", but there are still messages to be downloaded, they will be memorized and downloaded at next visit to group or at next sync.
Synchronized group (new headers) : when ticked and you leave the group, that has a sync method set as "new headers download" , while still downloading messages, the messages will be memorized and the downloading will restart at next visit of the group or at the time of next sync.
Synchronized group ( headers +bodies) : when ticked and you leave the group, that has a sync method set as "download headers and bodies", while still downloading messages, the messages will be memorized and the downloading will restart at next visit of the group or at the time of next sync.
Ignore read messages : when ticked the messages that were marked read but not downloaded yet are ignored.
Always ask confirmation when leaving group : when ticked and you are leaving the group while messages are downloaded you will get a confirmation box. You will get the choice to memorize the messages to be downloaded or to ignore the messages.