I encountered the same problem. Maybe the attached patch could be used?
Arne
--- sendmail-8.13.8/sendmail/srvrsmtp.c 2007-09-24 15:46:20.000000000 +0200
+++ build-tree/sendmail-8.13.8/sendmail/srvrsmtp.c 2007-09-24 15:47:01.000000000 +0200
@@ -1552,7 +1552,7 @@
break;
}
- if (ismore)
+ if (ismore && !(strlen(q)==1 && q[0]=='='))
{
/* could this be shorter? XXX */
# if SASL >= 20000
