EQS-HV: ADTRAN Holdings Inc.: Bekanntmachung der Einberufung zur Hauptversammlung am 08.05.2024 in Huntsville/Alabama, Vereinigte Staaten, www.virtualshareholdermeeting.com/ADTN2024 mit dem Ziel der europaweiten Verbreitung gemäß §121 AktG

NOTICE HEREBY IS GIVEN that the 2024 Annual Meeting of Stockholders (the “Annual Meeting”) of ADTRAN Holdings, Inc. (the “Company”) will be held on Wednesday, May 8, 2024, at 10:30 a.m., Central Time, via live webcast. You can participate in the meeting by visiting https://adtran.hvanmeldung.online and entering the shareholder number and password included on your proxy card. If you hold your shares through an intermediary, such as a bank or broker, and do not have a shareholder number and password, please contact the bank or broker or our ADEUS hotline (see below) to request a proxy card. Please log in to the website by 10:15 a.m., Central Time, on the day of the meeting. There is no physical location for the Annual Meeting.

The Annual Meeting is being held for the purposes of considering and voting upon:

1. A proposal to elect eight directors to serve until the 2025 Annual Meeting of Stockholders;

2. A proposal to approve the adoption of the ADTRAN Holdings, Inc. 2024 Employee Stock Incentive Plan;

3. A proposal to approve the adoption of the ADTRAN Holdings, Inc. 2024 Directors Stock Plan;

4. An advisory proposal with respect to the compensation of the Company’s named executive officers (“NEOs”), as described in the Compensation Discussion and Analysis, executive compensation tables and accompanying narrative in the attached Proxy Statement;

5. A proposal to ratify the appointment of PricewaterhouseCoopers LLP as the independent registered public accounting firm of the Company for the fiscal year ending December 31, 2024; and

6. Such other business as properly may come before the Annual Meeting or any adjournments thereof. The Board of Directors is not aware of any other business to be presented for a vote of the stockholders at the Annual Meeting.

The Board of Directors recommends that you vote FOR each of the eight director nominees; FOR the adoption of the ADTRAN Holdings, Inc. 2024 Employee Stock Incentive Plan; FOR the adoption of the ADTRAN Holdings, Inc. 2024 Directors Stock Plan; FOR the approval on an advisory basis of the compensation of the Company’s NEOs; and FOR the ratification of the appointment of PricewaterhouseCoopers LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2024. The Annual Meeting may be adjourned from time to time without notice other than announcement at the meeting or at adjournments thereof, and any business for which notice is hereby given may be transacted at any such adjournment.

Information relating to the above matters is set forth in the Proxy Statement. Stockholders of record at the close of business on March 11, 2024, are entitled to receive notice of and to vote during the Annual Meeting and any adjournments thereof.

Whether or not you plan to participate in the Annual Meeting, we urge you to review these materials carefully, which are available at https://materials.proxyvote.com/00486H. We also encourage you to vote by one of the following means:

By Internet: Go to the website https://adtran.hvanmeldung.online and follow the instructions. You will need the shareholder number and password included on your proxy card to vote by Internet. Contact your bank or broker or our ADEUS hotline (see below) to request a proxy card.

By Mail: You may request a hard copy of the proxy materials, including a proxy card, by following the instructions on your Notice. Contact your bank or broker or our ADEUS hotline (see below) to request a proxy card. If you request and receive a proxy card, please mark your selections on the proxy card, date and sign your name exactly as it appears on the proxy card and mail the proxy card to ADEUS Aktienregister-Service-GmbH, Hauptversammlung, Postfach 57 03 64, 22772 Hamburg, Germany. Mailed proxy cards must be received no later than May 7, 2024 in order to be counted for the Annual Meeting.

Contact our ADEUS hotline by telephone or email at

+49 (0) 89 - 2019 0365 or [email protected]

for questions regarding voting and using the online service.

You can submit questions in advance of the Annual Meeting by visiting https://adtran.hvanmeldung.online, entering your shareholder number and password, and using the “Questions for Management” feature. You can submit questions during the Annual Meeting by following the instructions on the meeting website. Management will answer pertinent questions in the “Investor Resources” section of our website at https://investors.adtran.com. The questions and answers will be available as soon as practicable after the Annual Meeting and will remain available for thirty (30) days after posting.

By order of the Board of Directors,