I think you will find that it occurs in preview mode only.

Greetings to everyone!

Another one bug according to Pegasus Mail 4.63 dialog windows (in version 4.62 I didn't face such a bug and faced after update to 4.63 only).

Let's open Pegasus Mail Preferences and Options dialog (Tools > Options).

First time the dialog window opens in normal (not maximized or minimized) state but without the ability to move it, change it's size and without window buttons (three buttons in the right of window caption bar).

After that let's switch to the System messages window or to the Mail Folders window and back to the Preferences windows so Preferences window will become maximized and window buttons will appear.

After such a manipulation we can unmaximize, change size and position of the Preferences window or maximize it back.

The same behavior is applicable to any other Pegasus Mail 4.63 window no matter what the window exactly is.

Window buttons randomly disappear and windows often become frozen (impossible to change window size or position).

This does not happen in my installation so I suspect other factors are involved.

Could you give details of how your configuration is at the start - what windows are maximised, and preview/list mode setting?