Rule 425 filing

Third Quarter 2010

Earnings Conference Call

November 16, 2010

Filed by Primus Telecommunications Group, Incorporated

Pursuant to Rule 425 under the Securities Act of 1933

Subject Company: Arbinet

Corporation

Commission File No.: 000-51063

Safe Harbor

In connection with the proposed merger, Primus Telecommunications Group, Incorporated (“Primus”) will file with the Securities and Exchange Commission (“SEC”) a Registration

Statement on Form S-4 that will include a preliminary proxy statement of Primus and Arbinet Corporation (“Arbinet”) that also constitutes a preliminary prospectus of Primus. A

definitive joint proxy statement/prospectus will be sent to security holders of both Arbinet and Primus seeking their approval with respect to the proposed merger. Primus and Arbinet

also plan to file other documents with the SEC regarding the proposed transaction. INVESTORS AND SECURITY HOLDERS ARE URGED TO CAREFULLY READ THE

JOINT PROXY STATEMENT/PROSPECTUS AND OTHER DOCUMENTS FILED WITH THE SEC WHEN THEY BECOME AVAILABLE, BECAUSE THEY WILL

CONTAIN IMPORTANT INFORMATION. Investors and security holders may obtain a free copy of the joint proxy statement/prospectus (when it becomes available) and other

documents filed by Primus and Arbinet with the SEC, without charge, at the SEC’s web site at www.sec.gov. Copies of the joint proxy statement/prospectus, once available, and each

company’s SEC filings that will be incorporated by reference in the joint proxy statement/prospectus may also be obtained for free by directing a request to: (i) Primus 703-748-8050, or

(ii) Arbinet (Andrea Rose/Jed Repko Joele Frank, Wilkinson Brimmer Katcher (212) 355-4449).

Arbinet, Primus, and their respective directors, executive officers and other members of their management and employees may be deemed to be “participants” in the solicitation of

proxies from their respective security holders in connection with the proposed merger. Investors and security holders may obtain information regarding the names, affiliations and

interests of Primus’s directors, executive officers and other members of its management and employees in Primus’s Annual Report on Form 10-K for the year ended December 31, 2009,

which was filed with the SEC on April 5, 2010, and amended in a Form 10-K/A filed with the SEC on April 28, 2010, Primus’s proxy statement for its 2010 annual meeting, which was

filed with the SEC on June 14, 2010, and any subsequent statements of changes in beneficial ownership on file with the SEC. Investors and security holders may obtain information

regarding the names, affiliations and interests of Arbinet’s directors, executive officers and other members of their management and employees in Arbinet’s Annual Report on Form 10-

K for the year ended December 31, 2009, which was filed with the SEC on March 17, 2010, Arbinet’s proxy statement for its 2010 annual meeting, which was filed with the SEC on April

30, 2010, and any subsequent statements of changes in beneficial ownership on file with the SEC. These documents can be obtained free of charge from the sources listed above.

Additional information regarding the interests of these individuals will also be included in the joint proxy statement/prospectus regarding the proposed transaction when it becomes

available.

This document and related verbal statements include “forward-looking statements” as defined by the Securities and Exchange Commission. All statements, other than statements of

historical fact, included herein that address activities, events or developments that Arbinet or Primus expects, believes or anticipates will or may occur in the future, including anticipated

benefits and other aspects of the proposed merger, are forward-looking statements. These forward-looking statements are subject to risks and uncertainties that may cause actual results

to differ materially. Risks and uncertainties that could affect forward-looking statements include, but are not limited to, the following: the risk that the acquisition of Arbinet may not be

consummated for reasons including that the conditions precedent to the completion of the acquisition may not be satisfied; the possibility that the expected synergies from the proposed

merger will not be realized, or will not be realized within the anticipated time period; the risk that Primus’s and Arbinet’s businesses will not be integrated successfully; the possibility of

disruption from the merger making it more difficult to maintain business and operational relationships; any actions taken by either of the companies, including, but not limited to,

restructuring or strategic initiatives (including capital investments or asset acquisitions or dispositions); the ability to service substantial indebtedness; the risk factors or uncertainties

described from time to time in Arbinet’s filings with the Securities and Exchange Commission; and the risk factors or uncertainties described from time to time in Primus’s filings with

the Securities and Exchange Commission (including, among others, those listed under captions titled “Management’s Discussion and Analysis of Financial Condition and Results of

Operations — Liquidity and Capital Resources — Short- and Long-Term Liquidity Considerations and Risks;” “— Special Note Regarding Forward-Looking Statements;” and “Risk

Factors” in Primus’s annual report on Form 10-K and quarterly reports on Form 10-Q) that cover matters and risks including, but not limited to: (a) a continuation or worsening of

global recessionary economic conditions, including the effects of such conditions on our customers and our accounts receivables and revenues; (b) the general fluctuations in the

exchange rates of currencies, particularly any strengthening of the United States dollar relative to foreign currencies of the countries where we conduct our foreign operations; (c) the

possible inability to raise additional capital or refinance indebtedness when needed, or at all, whether due to adverse credit market conditions, our credit profile or otherwise; (d) a

continuation or worsening of turbulent or weak financial and capital market conditions; (e) adverse regulatory rulings or changes in the regulatory schemes or requirements and regulatory

enforcement in the markets in which we operate and uncertainty regarding the nature and degree of regulation relating to certain services; and (f) successful implementation of cost

reduction efforts. Readers are cautioned not to place undue reliance on forward-looking statements, which speak only as of their dates. Except as required by law, neither Arbinet nor

Primus intends to update or revise its forward-looking statements, whether as a result of new information, future events or otherwise.

Important

Information

and

Where

Find

Participants

the

Solicitation

Forward-Looking

Statements

Q3 and YTD 2010 Highlights

Notes:

All results of operations exclude Discontinued Operations and severance unless otherwise specified.

1. EBITDA excludes impact of severance expenses, $4.2 million in Q310 and $1.8 million in Q110 and is a non-GAAP financial measure. Definitions and reconciliations between

non-GAAP measures and relevant GAAP measures are available in the Appendix and in the Company’s periodic SEC filings.

2. Free Cash Flow is defined as Cash Flow from Operating Activities less Capital Expenditures.

(US$ 000s)

Q309

Q310

Change

Q309

Q310

Change

Revenue

$194.9

$188.2

($6.7)

$560.2

$575.8

$15.6

Gross Margin

68.1

67.3

(0.8)

196.4

209.0

12.6

Gross Margin %

34.9%

35.8%

0.9%

35.1%

36.3%

1.2%

Adjusted EBITDA

(1)

$21.2

$20.0

($1.2)

$60.7

$65.7

$5.1

EBITDA %

10.9%

10.6%

-0.3%

10.8%

11.4%

0.6%

Capex

3.9

6.4

2.5

9.5

16.7

7.2

Free Cash Flow

(2)

9.1

14.5

5.4

30.3

20.3

(10.0)

Cash Balance

$41.9

$49.6

$7.7

$41.9

$49.6

$7.7

Quarter ended

YTD

The Primus Portfolio –

Sum of the Parts

Adjusted

EBITDA

(US$ 000s)

Revenue

EBITDA

(1)

Capex

less Capex

Canada

$172.4

$34.9

$7.3

$27.6

Australia

205.7

29.8

7.6

22.2

Global Wholesale

137.6

3.2

0.1

3.1

Sub-Total

$515.7

$67.9

$15.0

$52.9

US Retail

$38.8

$4.1

$0.8

$3.3

Brazil

21.3

1.3

0.8

0.4

Corporate / India

(7.6)

$575.8

$65.7

$16.7

$49.0

Discontinued Operations

36.4

(0.4)

0.3

(0.8)

Severance

(6.1)

Total

$612.2

$59.2

$17.1

$42.2

YTD Q310

Total before

Discontinued Operations

Canada

30%

Australia

35%

Wholesale

24%

Brazil

Canada

48%

Australia

41%

Wholesale

Brazil

Notes:

1. A non-GAAP financial measure. Definitions and reconciliations between non-GAAP measures and relevant GAAP measures are available in the Appendix and in the Company’s periodic SEC filings.

Primus Canada Highlights

•

Headquartered in Toronto,

Ontario

•

C$240M revenue in annualized

revenue

•

800 employees

•

Data centers and sales offices in

BC, Alberta, and Ontario

•

450K customers across the

country

•

70 DSLAMs

(primarily in

Ontario & Quebec)

•

Provide on-net equal access to

~90% of population

•

Call centers in Ontario (Ottawa)

and New Brunswick

Primus Australia Highlights

•

Headquartered in Melbourne

•

A$305 million in annualized

revenue

•

575 employees

•

3 Data Centers in Melbourne

and Sydney

•

Offices in Melbourne, Sydney,

Adelaide, Brisbane and Perth

•

250K customers located in all

territories

•

5 carrier-grade voice switches

and 66 points of interconnect

•

281 DSLAMs

primarily in major

cities and surrounding suburbs

•

Central business district metro

fiber in Sydney and Melbourne

Global Wholesale Services

Key

Combination

Considerations:

•

Increased scale in carrier services market

•

Benefits

thexchange

–

Arbinet’s

world-class

telecommunications

trading

platform

•

Added products and services and enhanced access to certain international routes

•

Complementary market presence

•

Synergy potential of $3 million to $7 million (when fully integrated)

•

Consolidation benefits for network and facilities

Combined

PRIMUS

Before

(all figures in millions and annualized, except customers)

Carrier

Arbinet

Synergies

Revenue

(1)

$183.4

$330.0

$513.4

Gross Margin

(1)

$10.8

$25.0

$35.8

Gross Margin %

5.9%

7.6%

7.0%

Customers

262

1,237

Minutes of Use

4,340

12,667

(1) Revenue and Gross Margin are presented net of Bad Debt allowance.

YTD Q310 Annualized

Financial Summary

Revenue

Adjusted EBITDA

(1) (2)

Capital Expenditures

Free

Cash

Flow

(1)

($ Millions)

$195

$203

$193

$195

$188

$50

$100

$150

$200

$250

Q309

Q409

Q110

Q210

Q310

-3.3%

% Sequential

Change

5.9 %

4.0%

-4.7%

0.8%

3.4%

% of

Revenue

2.0%

2.7%

2.5%

3.0%

10.6%

% of

Revenue

10.7%

10.8%

11.8%

11.7%

$14

($7)

$13

-$10

-$5

$10

$15

$20

Q309

Q409

Q110

Q210

Q310

$21

$22

$23

$20

$10

$15

$20

$25

Q309

Q409

Q110

Q210

Q310

$10

Q309

Q409

Q110

Q210

Q310

7.4%

% of

Revenue

4.7%

3.0%

6.7%

(3.6)%

(1)

A non-GAAP financial measure. Definitions and reconciliations between non-GAAP measures and relevant GAAP measures are available in the Appendix and in the Company’s periodic SEC filings.

(2)

Adjusted EBITDA excludes impact of severance charges in Q109 ($1.8 million) and Q310 ($4.2 million).

Note:

All results of operations exclude Discontinued Operations unless otherwise specified.

Canada Overview

Net Revenue

Adjusted EBITDA

(1)

(0.8)%

59.1

(CAD$)

$63.1

$62.1

$59.8

$59.6

Sequential Change

(2.0)%

(1.6)%

(3.6)%

(0.4)%

20.0%

(3.3)%

$11.8

(CAD$)

$12.8

$11.8

$12.1

$12.2

Sequential Change

(7.9)%

(7.8)%

2.5%

0.8%

% of Revenue

20.3%

19.1%

20.2%

20.5%

($Millions)

Most profitable business unit

in the portfolio

Stable EBITDA averaging

20% of net revenue despite

declining revenues

40% and 7% growth year-

over-year in Hosted IP/PBX

and data center revenues,

respectively

Effective cost controls helped

offset the impact of declining

revenues on EBITDA and free

cash flow

$56.9

$58.0

$57.5

$58.7

$57.4

$25

$50

$75

Q309

Q409

Q110

Q210

Q310

$11.3

$12.0

$11.6

$11.2

$11.6

$10

$15

$20

Q309

Q409

Q110

Q210

Q310

(1)

A non-GAAP financial measure. Definitions and reconciliations between non-GAAP measures and relevant GAAP measures are available in the Appendix and in the Company’s periodic SEC filings.

Australia Overview

Net Revenue

Adjusted EBITDA

(1)

(0.8)%

$75.8

(AUS$)

$76.5

$75.9

$77.3

$76.4

Sequential Change

(0.9)%

(0.8)%

1.9%

(1.2)%

13.2%

(2.9)%

$10.0

(AUS$)

$9.8

$9.7

$12.9

$10.3

Sequential Change

(10.1)%

(1.0)%

33.0%

(20.2)%

% of Revenue

12.9%

12.8%

16.6%

13.5%

($Millions)

Stable revenue stream

Declining residential revenue

replaced by higher margin

business revenue

46% growth year-over-year in

data center revenues and 6%

growth for business revenues in

aggregate

Adjusted EBITDA of 13.2% of

net revenue in Q310 versus

12.9% in Q309

$68.4

$69.9

$63.7

$69.0

$67.5

$60

$64

$68

$72

Q309

Q409

Q110

Q210

Q310

$9.0

$9.1

$11.6

$8.8

$8.2

$10

$12

$14

Q309

Q409

Q110

Q210

Q310

(1) A non-GAAP financial measure. Definitions and reconciliations between non-GAAP measures and relevant GAAP measures are available in the Appendix and in the Company’s periodic SEC filings.

Global Wholesale Overview

Net Revenue

Gross Margin %

(1)

$53.6

$54.9

$46.5

$49.2

$41.9

$20

$40

$60

$80

Q309

Q409

Q110

Q210

Q310

4.1%

3.9%

3.7%

4.9%

5.2%

0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

6.0%

Q309

Q409

Q110

Q210

Q310

(1)

non-GAAP

financial

measure.

Gross

Margin

defined

Net

Revenue

less

costs

revenue

divided

Net

Revenue.

(14.9)%

Sequential Change

6.5%

2.5%

(15.3)%

5.8%

($Millions)

Gross margins, as a percentage

of net revenue, improved 110

basis points to 5.2% in Q310

versus Q309 as we focused on

higher margin US domestic

terminations

Summer seasonality in Europe

had expected effect on

quarterly traffic

Focus on profitability vs.

Revenue drove decision to

prune less profitable traffic

Primus’

Other Businesses

United States:

Net Revenue for the quarter decreased $4.1 million year over year to $12.1

million

Adjusted EBITDA for the quarter decreased $1.6 million year over

year to

$0.9 million

Brazil:

Net Revenue for the quarter increased BRR 8.2 million year over year to BRR

15.9 million

Adjusted EBITDA for the quarter remained flat year over year as the

significant increase in revenue was derived from low-margin reseller voice

services

Europe Retail:

All European retail operations classified as “Discontinued Operations”

in the

financial statements

$6.2 million (non-cash) impairment charge for goodwill and long-lived assets,

primarily intangibles established as part of fresh start accounting

Adjusted EBITDA of (€2K) and (€71K) for the third quarters 2010 and 2009,

respectively

Foreign Currency Effects

More than 80% of revenue generated outside US

Natural in-country currency hedge

Revenue and costs are largely denominated in each country’s local currency

Impact of currency fluctuations driven by US dollar

remittances from foreign units to service debt

.5688

0.9617

0.9023

Q310

0.5536

0.9602

0.9036

Q110

0.5559

0.9731

0.8835

Q210

0.5800

0.9900

As of

11/15/10

Q309

Q409

AUD $

0.8323

0.9087

CAN $

0.9097

0.9460

BRR

0.5335

0.5728

Average Exchange Rate to US$

Balance Sheet

($US Millions)

Q309

Q409

Q110

Q210

Q310

Total Debt / LTM Adjusted EBITDA

3.30x

3.15x

2.99x

2.79x

2.81x

Net Debt / LTM Adjusted EBITDA

2.76x

2.63x

2.38x

2.40x

2.24x

Interest Coverage Ratio

2.50x

1.77x

2.45x

2.69x

2.31x

Note:

All results of operations exclude Discontinued Operations and severance unless otherwise specified.

Cash balance of $49.6 million at September 30, 2010

Principal amount of total debt at 9/30/10 was $245.9

million compared to $246.3 million at 6/30/10

Improving leverage ratios

(1)

A non-GAAP financial measure. Definitions and reconciliations between non-GAAP measures and relevant GAAP measures are available in the Appendix and in the Company’s

periodic SEC filings.

Adjusted EBITDA

Adjusted EBITDA, as defined by us, consists of net income (loss) before

reorganization items, net, share-based compensation expense, depreciation and

amortization, asset impairment expense, gain (loss) on sale or disposal of assets,

interest expense, amortization or accretion on debt discount or premium, gain (loss) on

early extinguishment or restructuring of debt, interest income and other income

(expense), gain (loss) from contingent value rights valuation, foreign currency

transaction gain (loss), income tax benefit (expense), income (expense) attributable to

the non-controlling interest, income (loss) from discontinued operations, net of tax, and

income (loss) from sale of discontinued operations, net of tax. Our definition of

Adjusted EBITDA may not be similar to Adjusted EBITDA measures presented by

other companies, is not a measurement under generally accepted accounting principles

in the United States, and should be considered in addition to, but not as a substitute for,

the information contained in our statements of operations.

We believe Adjusted EBITDA is an important performance measurement for our

investors because it gives them a metric to analyze our results exclusive of certain non-

cash items and items which do not directly correlate to our business of selling and

provisioning telecommunications services. We believe Adjusted EBITDA provides

further insight into our current performance and period to period performance on a

qualitative basis and is a measure that we use to evaluate our results and performance

of our management team.

Free Cash Flow

Free Cash Flow, as defined by us, consists of net cash provided by (used in) operating

activities before reorganization items less net cash used in the purchase of property and

equipment. Free Cash Flow, as defined above, may not be similar to Free Cash Flow

measures presented by other companies, is not a measurement under generally

accepted accounting principles in the United States, and should be considered in

addition to, but not as a substitute for, the information contained in our consolidated

statements of cash flows.

We believe Free Cash Flow provides a measure of our ability, after purchases of

capital and other investments in our infrastructure, to meet scheduled debt principal

payments. We use Free Cash Flow to monitor the impact of our operations on our cash

reserves and our ability to generate sufficient cash flow to fund our scheduled debt

maturities and other financing activities, including discretionary refinancings and

retirements of debt. Because Free Cash Flow represents the amount of cash generated

or used in operating activities less amounts used in the purchase of property and

equipment before deductions for scheduled debt maturities and other fixed obligations

(such as capital leases, vendor financing and other long-term obligations), you should

not use it as a measure of the amount of cash available for discretionary expenditures.

Non-GAAP Measures

Note:

All results of operations excluded Discontinued Operations unless otherwise specified.

Three Months

Ended

September 30,

June 30,

September 30,

2010

2009

NET INCOME (LOSS) ATTRIBUTABLE TO

PRIMUS TELECOMMUNICATIONS GROUP, INCORPORATED$

5,080

(13,038)

2,165

Reorganization items, net

307

Share-based compensation expense

(12)

117

307

Depreciation and amortization

13,641

18,194

18,740

(Gain) loss on sale or disposal of assets

(189)

Interest expense

8,602

8,733

8,747

Accretion (amortization) on debt premium/discount, net

(Gain) loss on early extinguishment of debt

(164)

Interest and other (income) expense

(254)

(153)

(160)

(Gain) loss from Contingent Value Rights valuation

(33)

382

4,229

Foreign currency transaction (gain) loss

(14,006)

9,623

(13,448)

Income tax (benefit) expense

(3,238)

(1,883)

(2,121)

Income (expense) attributable to the non-controlling interest

(106)

210

(Income) loss from discontinued operations,

net of tax

5,464

1,528

2,110

(Gain) loss from sale of discontinued operations,

net of tax

389

(193)

110

ADJUSTED EBITDA

15,753

22,896

21,232

NET CASH PROVIDED BY (USED IN)

OPERATING ACTIVITIES BEFORE REORGANIZATION ITEMS$

20,865

(1,140)

12,992

Net cash used in purchase of property

and equipment

(6,410)

(5,824)

(3,886)

FREE CASH FLOW

14,455

(6,964)

9,106