<PAGE>   1
                                                                   EXHIBIT 10.18

                             ASSIGNMENT OF SUBLEASE

      This Assignment of Sublease ("Assignment") is entered into on November
24, 1999 between and among California Casualty Management Company, a California
corporation ("Sublessor"), True Genesis, Inc., a California corporation
("Assignor") and Eloquent, Inc., a Delaware corporation ("Assignee").

RECITALS

A.    WHEREAS, Sublessor and Assignor (as Sublessee) entered into a written
Sublease Agreement dated June 1, 1999 (the "Sublease") by which Sublessor
sublet to Assignor and Assignor sublet from Sublessor Suite 161 in 2000 Alameda
de las Pulgas, San Mateo, California, consisting of approximately 2,621
rentable square feet.

B.    WHEREAS, Sublessor is the Tenant under a written Office Lease dated as of
March 18, 1998 (the "Prime Lease") wherein OTR ("Prime Landlord") leased to
Sublessor certain real property located in 2000 Alameda de las Pulgas, City of
San Mateo, County of San Mateo, State of California, including Suite 161. Any
term in this Assignment with an initial capital letter, not specifically
defined herein, shall have the meaning given it in the Prime Lease or Sublease.

C.    WHEREAS, Assignor desires to assign all its right, title, and interest in
the Sublease to Assignee in accordance with Section 8 of the Sublease.

AGREEMENT

1.    Effective Date. The assignment made hereby shall take effect on
December 1, 1999, and Assignor shall give possession of the Sublet Premises to
Assignee on that date.

2.    Assignment and Assumption. Assignor assigns and transfers to Assignee all
its right, title, and interest in the Sublease, and Assignee accepts the
assignment and assumes and agrees to perform, from the date this assignment
becomes effective, as a direct obligation to Sublessee, all the provisions of
the Sublease.

3.    Sublessor's Consent. Subject to Prime Landlord granting its consent to
this Assignment, Sublessor consents to this Assignment in accordance with
Section 8 of the Sublease.

4.    Prepaid Rent/Security Deposit. Concurrent with the execution of this
Assignment, Assignee shall provide Sublessor with a security deposit in an
amount equal to three month's Monthly Rent ($27,520), which shall be refunded
to Assignee upon full satisfaction of the terms and conditions of the Sublease.
In addition, Assignee shall provide the first month's Monthly Rent in the
amount of $9,173 to Sublessor upon execution of this Assignment. Sublessor
shall return a security deposit in an amount equal to three month's Monthly
Rent ($27,520) to Assignor upon execution of the Assignment.

<PAGE>   2

5.   Notices.  All notices, demands, requests, approvals, payments and other
communications between the parties (collectively "Notices") shall be in writing
at the addresses set forth below. Notices shall be sufficiently given if, and
shall be deemed not given unless, deposited in the United States mail postage
prepaid in certified or registered form, return receipt requested, properly
deposited with Federal Express, or another similar overnight carrier, or
personally served or delivered.

     If to Sublessor:

          California Casualty Management Company
          Real Estate Department
          1650 Telstar Drive
          Colorado Springs, CO 80920-1004
          Attn: Manager of Real Estate

     If to Assignor:

          True Genesis, Inc.
          2000 Alameda de las Pulgas
          San Mateo, CA 94403

     If to Assignee:

          Eloquent, Inc.
          2000 Alameda de las Pulgas
          San Mateo, CA 94403

     If notices are personally delivered, copies shall also be mailed. Notices
shall be deemed given when personally served or delivered, two days after
deposit with Federal Express, or other similar overnight carrier, or five days
after deposit in the United States mail.

<PAGE>   3
     IN WITNESS WHEREOF, the parties have executed this Assignment effective as
of the date first set forth above.


          SUBLESSOR:                    California Casualty Management Company

Date 12/1/99                            By: /s/ [SIGNATURE ILLEGIBLE]
                                           -----------------------------------
                                        Its: Asst VP & Real Estate Manager


          ASSIGNOR:                     True Genesis, Inc.

Date 11-24-99                           By: /s/ [SIGNATURE ILLEGIBLE]
                                           -----------------------------------
                                        Its: Director of Operations

          ASSIGNEE:                     Eloquent, Inc.

Date 11-24-99                           By: /s/ [SIGNATURE ILLEGIBLE]
                                           -----------------------------------
                                        Its: CFO


<PAGE>   4
                           CONSENT OF PRIME LANDLORD


     1.    OTR, an Ohio general partnership ("Prime Landlord"), landlord under
the Prime Lease, consents to the foregoing Assignment of Sublease for Suite 161
in 2000 Alameda de las Pulgas, between California Casualty Management Company,
True Genesis, Inc., and Eloquent, Inc.; provided, however, that except as
specifically provided herein, this Consent shall not: (1) constitute a waiver,
amendment or modification of any term or condition of the Prime Lease with
respect to either Sublessor or Sublessee; or (2) limit the obligations of
Sublessor or the rights of Prime Landlord under the Lease; or (3) make Prime
Landlord a party to the Sublease or the Assignment.

     2.   Prime Landlord represents that (i) it is not in default under the
Prime Lease; (ii) to the best of its knowledge, Sublessor is not in default
under the Prime Lease; (iii) Sublessor has not paid rent for more than one
month in advance; and (iv) Sublessor's last rental payment was made
____________, 19___ for the month of ________, 19____.


                                   OTR, an Ohio general partnership

Date  12/20/99                     By: /s/ [SIGNATURE ILLEGIBLE]
                                       ----------------------------
                                   Its: Asset Management Officer