You are correct that the ".consulting" is not one of the default domains allowed in a Jive instance, however as you also mention this can be modified via the mail.valid.tld.pattern system property. For reference the default domains are as follows:
I am on a hosted instance so you will probly have to do it for me.
If you are on Jive Cloud instance, please submit a case in your customer group and the next available support engineer can assist in evaluating this type of change in your instance. However, if you are on a Jive Custom release, you should have access to this as an admin user via your admin console.