adjust the MX records for ibm.com so that they point to your SMTP gateway
One important remark is that the shortname field can contain e-mail aliases and is multi-value. The internet address field in a person document is single value and contains the ‘official’ e-mail address as it will be sent out.
You can also update groups and mail-in databases if they have an internet address. But with these docs, you cannot use aliases.