The 'from' field in the email builder has gotten an extra option lately it seems to accept local addresses, see below. This is set by default to 'true', I believe it has to be 'false' since it breaks previous implementations where the email address is checked because it now accepts addresses that do not contain @ etc. and are not valid.
<datatype base="internetaddress" xmlns="
http://www.mmbase.org/xmlns/datatypes">
<property name="maxAddress" value="1" />
<property name="local" value="true" />
<required value="true" />
<maxLength value="255" />
</datatype>