<PAGE>

                                                                   EXHIBIT 10.30
                                  NONNEGOTIABLE
                                 PROMISSORY NOTE



Cdn. $100,000                                              Issued:  May 11, 2001
Principal Amount                                    Maturity Date:  July 8, 2001


     FOR VALUE RECEIVED, each of Voice Mobility International, Inc., a Nevada
corporation and Voice Mobility Inc., a Canada Business Corporations Act
corporation (each a "Maker" and collectively the "Makers"), hereby jointly and
severally promise to pay to Interior Holdings Ltd. (the "Payee"), the principal
amount ("Principal Amount") of One Hundred Thousand Dollars (Cdn.$100,000),
according to the following terms and conditions. Except as may be required by
applicable law, no interest shall accrue or be payable with respect to the
outstanding principal amount of this Note. This instrument is not negotiable or
assignable by Payee except to a Permitted Transferee as defined below. All
references to currency herein refer to Canadian Dollars unless otherwise noted.

     1.   FEES AND PAYMENT SCHEDULE.

          All unpaid portions of the Principal Amount and a fee of $3,500
remaining on this Note shall be due and payable on the earlier of July 8, 2001
(the "Maturity Date") or the receipt of proceeds from Makers' next bona fide
third party equity financing.

     2.   DEFAULT. For purposes of this Note, a "Default" shall be deemed to
have occurred upon any of the following events:

          (a)  A failure by Makers to pay any Principal or Fees owing under this
Note when due on the Maturity Date;

          (b)  Any Maker shall make an assignment for the benefit of creditors,
or if a receiver of any Maker's property shall be appointed, or if a petition in
bankruptcy or for the reorganization under any Chapter of any Federal, State or
Provincial Bankruptcy Act or other similar proceeding under law for relief of
debtors shall be filed by or against any Maker, or if any lien of attachment,
execution, lien, or claim of lien be placed against all or any portion of the
assets of the Makers and is not cleared from the record or reasonably bonded
against within ninety (90) days after it has been filed; unless

          (c)  Any such failure or action by Makers under Sections 3(a) and (b)
shall not have been cured within fifteen (15) days of receipt of a notice from
Payee specifying the alleged Default or failure; and

          (d)  Provided, however, that no delay or omission on the part of Payee
in exercising any right hereunder shall operate as a waiver of such right or of
any right under this Note.

                                       1
<PAGE>

A waiver on any one occasion shall not be construed as a bar to or waiver of any
right or remedy on any future occasion. Except as set forth in this Section 3,
Makers hereby expressly waive any presentment, demand, protest, notice of
protest or other notice of any kind and hereby expressly waive and covenants not
to assert any appraisement, stay, extension, redemption or similar laws, now or
at any time hereafter enforce, which might delay, prevent or otherwise impede
the enforcement of this Note.

     3.   REMEDIES. Upon the occurrence of a Default and unless such Default
shall have been cured in accordance with the terms of this Note, the Payee may
declare the entire unpaid Principal Amount and all other amounts due hereunder
immediately due and payable. The rights and remedies available to Payee under
this Note shall be cumulative and in addition to any other rights or remedies
that Payee may be entitled to pursue at law or in equity. The exercise of one or
more of such rights or remedies shall not impair Payee's right to exercise any
other right or remedy at law or in equity.

     4.   ASSIGNMENT. The rights and obligations of the parties hereunder shall
not be assignable by either party without the consent of the other except Payee
may assign its rights to a Permitted Transferee. For purposes hereof a Permitted
Transferee, shall be (x) a corporation, partnership or other entity, which is a
successor by merger, reorganization, consolidation or similar corporate
transaction, or in which the members of the Payee or any member of the immediate
family of the Payee are the sole owners of the equity interests in such
corporation, partnership or other entity, (y) any member of the Payee or any
adult member of such member's immediate family or any trust established for the
beneficiary of any such persons or, (z) in the case of the dissolution or
liquidation of the Payee, or in the death of any individual Permitted
Transferee, the successor to the same by will, the laws of intestate succession
or the corporate laws of the state or province having jurisdiction over the
matter. To the extent such assignments are allowed, the provisions of this Note
shall be binding upon and inure to the benefit of the parties hereto and their
respective designees, heirs, legal representatives, successors and assigns, to
the extent provided herein.

     5.   COSTS. Makers shall pay, on demand, any and all costs and expenses,
including reasonable attorneys' fees, incurred by Payee in connection with a
Default and the collection of any portion of the Principal Amount and Fees
accrued thereon. Makers shall pay Payee an additional fee of $3,500 on the
Maturity Date.

     6.   NO CONTINUING WAIVER. The waiver of a Default shall not constitute a
continuing waiver or a waiver of any subsequent Default. Makers hereby waive
presentment, demand, dishonor and notice of nonpayment.

     7.   NOTICE. All notices, requests, consents and other communications which
may be desired or required hereunder shall be in writing, and shall be deemed to
have been duly given on the date of delivery if delivered in person to the party
named below, or three (3) days after mailing if deposited in the United States
or Canadian mail, first class, registered or certified mail, return receipt
requested, with postage prepaid, addressed as follows:

                                       2
<PAGE>

          If to Makers:      Voice Mobility International, Inc. and
                             Voice Mobility Inc.
                             180 - 13777 Commerce Parkway
                             Richmond, B.C. V6V 2X3
                             Attention:  James Hewett, CFO
                             Telecopier: 604-232-4826

          If to Payee:       Interior Holdings Ltd.
                             PO Box F-41573
                             Freeport, Bahamas

     8.   SEVERABILITY. If any provision of this Note or the application thereof
to any person or circumstance shall be held invalid or unenforceable to any
extent, the remainder of this Note and the application of any such provision to
other persons or circumstances shall not be affected thereby and shall be
enforced to the greatest extent permitted by law.

     9.   INTERPRETATION OF DOCUMENT. The parties hereto acknowledge and agree
that this Note has been negotiated arms length and between parties equally
sophisticated and knowledgeable in the matters dealt with in this Note. Each
party has had access to counsel of their selection. Accordingly, any rule of
law, court decision or other legal precedent that would require interpretation
of any ambiguities in this Note against the party that has drafted it is not
applicable and is waived.

     10.  GOVERNING LAW AND VENUE. This Note and the rights and obligations of
the parties hereunder and the persons subject hereto shall be governed by, and
construed and interpreted in accordance with, the laws of the Province of
British Columbia, without giving effect to the choice of law principles thereof.
Each party agrees that any proceeding relating to this Note shall be brought in
a state court in Nevada or provincial court of British Columbia and each party
consents to personal jurisdiction in any such action brought in any such court.

                              VOICE MOBILITY INTERNATIONAL, INC.,
                              a Nevada Corporation


                              By:    /s/ JAMES HEWETT
                                     ----------------
                              Name:  James Hewett
                              Title: CFO


                              VOICE MOBILITY INC.,
                              a Canada Corporations Act Corporation


                              By:    /s/ JAMES HUTTON
                                     ----------------
                              Name:  James Hutton
                              Title: CEO


                                       3