Document:

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                                                                   Exhibit 10.25

                         Intermedia Communications Inc.
                             3625 Queen Palm Drive
                             Tampa, Florida  33619

                                                 January 24, 2000

Digex, Incorporated
One Digex Plaza
Beltsville, Maryland  20705

Ladies and Gentlemen:

     In connection with the proposed public offering ("Offering") of Class A
                                                       --------
common stock of Digex, Incorporated ("Digex") as reflected in a registration
                                      -----
statement on Form S-1 which was filed with the Securities and Exchange
Commission on January 18, 2000 (File #333-94857), Intermedia Communications Inc.
("Intermedia") and Digex wish to confirm their understanding as set forth in
  ----------
this letter.

     Intermedia and Digex acknowledge that Digex will be required to use all of
the net proceeds of the Offering, if one is consummated, to purchase or
construct Telecommunications Related Assets (as defined in the 12-1/2% Senior
Discount Notes Indenture, dated May 14, 1996 (the "Indenture"), between
                                                   ---------
Intermedia and SunTrust Bank, Central Florida, National Association, as trustee)
within 270 days after the closing of the Offering.  Intermedia and Digex agree
that during such 270-day period:

1.   Intermedia, in consultation with the management of Digex, shall, from time
     to time, determine the amount of funds required by Digex to meet its
     working capital needs or to fund its operating losses ("Unrestricted Uses")
                                                             -----------------
     during the next calendar month.  Within five days of determination of the
     amount required by Digex for Unrestricted Uses, Intermedia shall provide to
     Digex a list of Telecommunications Related Assets having a purchase price
     at least equal to such amount to be purchased by Digex (the "Designated
                                                                  ----------
     Assets") and shall designate, and, if necessary, make arrangements with (on
     ------
     Digex's behalf), a vendor or vendors from which Digex should purchase the
     Designated Assets.  Digex shall purchase the Designated Assets from the
     vendor(s) designated by Intermedia from time to time as reasonably required
     to fund Unrestricted Uses, and Intermedia shall purchase from Digex, the
     Designated Assets at Digex's cost thereof promptly following each purchase.
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Digex, Incorporated
Page 2

2.   If on the 260th day after the closing of the Offering there remains an
     amount (the "Remaining Amount") of the net proceeds of the Offering that
                  ----------------
     has not been used by Digex to purchase or construct Telecommunications
     Related Assets, then Intermedia shall provide to Digex a list of Designated
     Assets, and, if necessary, make arrangements with (on Digex's behalf), a
     vendor or vendors from which Digex should purchase the Designated Assets.
     The purchase price of such Designated Assets from such designated vendor(s)
     shall at least equal the Remaining Amount.  Within five days after its
     receipt of such notice from Intermedia, Digex shall purchase the Designated
     Assets from the vendor(s) designated by Intermedia.  If and to the extent
     that the purchase price of such Designated Assets exceeds the Remaining
     Amount, Intermedia shall advance such difference to Digex prior to such
     purchase.  Promptly following any such purchase, Digex shall sell to
     Intermedia, and Intermedia shall purchase from Digex, the Designated Assets
     at Digex's cost thereof.

3.   Intermedia represents and warrants to Digex that Digex's use for
     Unrestricted Uses of a portion of the amounts received by it from
     Intermedia designated by Intermedia as unrestricted funds ("Unrestricted
                                                                 ------------
     Portion") in any purchase and sale transaction pursuant to paragraphs 1 or
     -------
     2 will not violate, or result in a default by Intermedia under, the
     provisions of the Indenture.  The amount of the Unrestricted Portion shall
     be determined based on a reasonable projection of Digex's need for funds
     for Unrestricted Uses during the period commencing on the date of such
     purchase and sale and ending on the first anniversary of the closing of the
     Offering.

4.   Digex represents, warrants and covenants to Intermedia that it shall use
     the net proceeds of the Offering only to purchase or construct
     Telecommunications Related Assets and as provided in this letter agreement.

5.   Each of Digex and Intermedia agrees to cooperate with the other, and to do,
     execute, acknowledge and deliver such further acts, instruments and
     assurances as shall be necessary or desirable to carry out the provisions,
     and the intents and purposes of this letter agreement.  Notwithstanding any
     of the procedures set forth in this letter agreement, with the consent of
     both parties, Intermedia may advance to Digex on a daily basis Digex's cash
     requirements for Unrestricted Uses and purchases of Telecommunications
     Related Assets.  In such circumstances, at the end of every calendar month,
     Intermedia shall prepare and provide to Digex a statement of reconciliation
     of all advances and expenditures made by Intermedia to Digex or on Digex
     behalf during the month-ended, and Digex shall make a corresponding
     transfer of funds to Intermedia.
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Digex, Incorporated
Page 3

     Please confirm your understanding and acceptance of the foregoing by
signing in the space provided below.

                                      Very truly yours,

                                      INTERMEDIA COMMUNICATIONS INC.

                                      By: /s/ DAVID C. RUBERG
                                         ___________________________
                                         Name:  David C. Ruberg
                                         Title: President and CEO

Agreed and Accepted
this 24th day of January 2000

DIGEX, INCORPORATED

By: /s/ MARK K. SHULL
   ________________________
   Name:  Mark K. Shull
   Title: President and CEO<PAGE>

                                                                   Exhibit 10.26

                         Intermedia Communications Inc.
                              3625 Queen Palm Drive
                              Tampa, Florida 33619

                                                     January 24, 2000

Digex, Incorporated
One Digex Plaza
Beltsville, Maryland  20705

Ladies and Gentlemen:

     In connection with the proposed public offering and sale (the "Offering")
                                                                    --------
of Class A Common Stock, par value $.01 per share, of Digex, Incorporated

("Digex") by Digex and Intermedia Communications Inc., as a selling stockholder
  -----
("Intermedia"), as reflected in the registration statement on Form S-1 filed
  ----------
with the Securities and Exchange Commission on January 18, 2000 (File #333-
94857), and any amendments thereto (the "Registration Statement"), Intermedia
                                         ----------------------
and Digex wish to confirm their understanding as set forth in this letter.

1.   Digex and Intermedia each hereby agrees to allocate and pay the fees and
     expenses associated with and arising from the Offering in proportion to the
     number of shares of Class A Common Stock to be sold by each of them in the
     Offering.  Such fees and expenses shall include, without limitation, those
     incurred in connection with (a) preparing, printing, duplicating, filing
     and distributing the Registration Statement, as originally filed and all
     amendments thereto (including all exhibits thereto), any preliminary
     prospectus or prospectus and any amendments or supplements thereto
     (including, without limitation, fees and expenses of Digex's accountants
     and counsel), (b) the issuance, transfer and delivery of the Shares to the
     underwriters of the Offering (the "Underwriters"), including any transfer
                                        ------------
     or other taxes payable thereon, (c) the qualification of the shares of
     Class A Common Stock to be sold in the Offering (the "Shares") under state
                                                           ------
     or foreign securities or Blue Sky laws, including the costs of printing and
     mailing a preliminary and final "Blue Sky Memorandum" and the fees of
     counsel in connection therewith and such counsel's disbursements in
     relation thereto, (d) listing of the Shares for quotation on the Nasdaq
     National Market System, (e) filing fees of the Securities and Exchange
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Digex, Incorporated
Page 2

     Commission and the NASD, (f) the cost of printing certificates representing
     the Shares, (g) the cost and charges of any transfer agent or registrar and
     (h) all costs and expenses of the Underwriters payable by Digex and/or
     Intermedia pursuant to the underwriting agreement for the Offering.

2.   With respect to any joint or several indemnification or contribution
     obligation of either Digex or Intermedia or any other losses, claims,
     damages or liabilities of either Digex or Intermedia (collectively

     "Damages") arising out of, or in any manner relating to or resulting from
      -------
     the Offering, Digex and Intermedia each hereby agrees to allocate and pay
     such Damages in proportion to the number of shares of Class A Common Stock
     to be sold by each of them in the Offering.

     Please confirm your understanding and acceptance of the foregoing by
signing in the space provided below.

                         Very truly yours,

                         INTERMEDIA COMMUNICATIONS INC.

                         By: /s/ DAVID C. RUBERG
                             -------------------
                             Name: David C. Ruberg
                             Title: President and CEO

Agreed and Accepted
this 24/th/ day of January 2000

DIGEX, INCORPORATED

By: /s/ MARK K. SHULL
    -----------------
    Name: Mark K. Shull
    Title: President and CEO

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