Please try the attached patch.
diff --git a/libmailutils/imapio/flags.c b/libmailutils/imapio/flags.c
index b84f4fb..02a20af 100644
--- a/libmailutils/imapio/flags.c
+++ b/libmailutils/imapio/flags.c
@@ -34,7 +34,7 @@ _imap4_attrlist[] =
{ "\\Flagged", MU_ATTRIBUTE_FLAGGED },
{ "\\Deleted", MU_ATTRIBUTE_DELETED },
{ "\\Draft", MU_ATTRIBUTE_DRAFT },
- { "\\Seen", MU_ATTRIBUTE_SEEN|MU_ATTRIBUTE_READ },
+ { "\\Seen", MU_ATTRIBUTE_READ },
};static int _imap4_nattr = MU_ARRAY_SIZE (_imap4_attrlist);
