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                                                                   EXHIBIT 10.16

               [LETTERHEAD OF DIGEX, INCORPORATED APPEARS HERE]



                                        July 9, 1999



Mr. Bryan T. Gernert
One Digex Plaza
Beltsville, Maryland 20705

Dear Bryan:

        This will confirm the changes we have agreed upon in your employment
arrangement with Digex as follows:

        (a) Your base salary is $200,000 per year and your annual bonus
opportunity is 60% of your base salary.

        (b) If the Digex initial public offering of common stock becomes
effective, you will receive an options to purchase 300,000 shares of Digex
common stock at an exercise price equal to $5.00 per share and an option to
purchase 100,000 common shares at exercise price equal to the initial public
offering price.  Options covering 25% of the shares will vest one year following
the date of grant and the balance will vest in equal quarterly installments over
the next three years so long as you continue to be employed by Digex.

        (c) Following the occurrence of a change of control, all unvested
installments of the options will vest if your employment is terminated by Digex
(other than for cause as defined herein) or, if earlier, one year following the
date of occurrence of the change of control if you continue to be employed by
Digex at that time.  In addition, in the event your employment is terminated by
Digex for any reason other than for cause within two years of the date of this
letter, your option[s] will be deemed to be vested for an aggregate of 200,000
shares (including any installment previously vested in accordance with the terms
of the option).

For purposes of this letter:

        "Change of Control" means: the sale, exchange or transfer of common
        stock of Intermedia or of Digex, whether in one transaction or a series
        of related transactions occurring within one year, which results in an
        accumulation of 50% or more of the outstanding shares of common stock
        (on a fully diluted basis) of
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               [LETTERHEAD OF DIGEX, INCORPORATED APPEARS HERE]



        Intermedia or of Digex in one holder or several affiliated holders (or
        any such transaction(s) occurring within six months that result in an
        accumulation of at least 35% of such shares of common stock (on a fully
        diluted basis)) or an event involving the sale or merger of Intermedia
        or of Digex or their respective assets which results in the holders of
        shares of common stock immediately prior to the occurrence of such sale
        or merger holding less than a majority of the outstanding shares of
        common stock immediately thereafter.

        "Cause" means: (i) any conduct or behavior by you that would reasonably
        be expected to have a material adverse affect on Intermedia's or Digex's
        business or reputation, (ii) commission by you of an act involving moral
        turpitude or dishonesty, including fraud, (iii) your material failure to
        reasonably perform your duties for Digex or (iv) your willful failure to
        perform or abide by any lawful directions or instructions of Digex
        consistent with your capacity as a senior executive of Digex.

        (d) Your existing Intermedia stock options shall continue in full force
and effect following consummation of the initial public offering of Digex common
stock.

        Except as amended hereby, the terms of your employment continue in full
force and effect.  If the foregoing is acceptable to you, please sign in the
space provided below and return to me one fully executed copy of this letter.
Nothing in this letter will be deemed to affect the at will status of your
continued employment by Digex.

                                        DIGEX, INCORPORATED

                                        By:      /s/ Mark Shull
                                           --------------------------
                                            Mark Shull, President and
                                             Chief Executive Officer

Agreement with terms
of letter confirmed:

/s/ Bryan T. Gernert
--------------------
  Bryan T. Gernert