You can refer its value in `wl-draft-config-alist'.
e.g.
-\(setq wl-draft-config-alist
+(setq wl-draft-config-alist
'(((string-match \".*@domain1$\" wl-draft-parent-folder)
(\"From\" . \"user@domain1\"))
((string-match \".*@domain2$\" wl-draft-parent-folder)