Файл callout.config.xml такого вида:
<?xml version="1.0" encoding="utf-8" ?>
<callout.config version="2.0">
<callout entity="opportunity" event="PostCreate">
<subscription assembly="CallOutSendMail2003.dll" class="SendMessageCallOut.Verify">
</subscription>
</callout>
<callout entity="task" event="PostCreate">
<subscription assembly="CallOutSendMail2003.dll" class="SendMessageCallOut.Verify">
</subscription>
</callout>
...............................
<callout entity="task" event="PostAssign">
<subscription assembly="CallOutSendMail2003.dll" class="SendMessageCallOut.Verify">
<prevalue>ownerid</prevalue>
<postvalue>ownerid</postvalue>
</subscription>
</callout>
...............................
</callout.config>