Wrong tab order on new message dialog.
When you open the new message dialog (v4.15.0 portable on Windows), the tab order is all wrong. The focus is initially on the Cancel button, by tabbing, it moves to the dmPublishOwnID checkbox, then payReplyCheckBox, immDownloadCheckBox, fromComboBox, then the Basic tab header, then finally subject (which should have been the initial focused control, IMHO).
AFAICT, the tabstops defined in the UI file look basically fine, but maybe the order there is wrong because of the nesting of the child controls, and the first entry needs to be the tabWidget or something? Dunno, no Qt expert.