EQS-HV: ADTRAN Holdings Inc.: Bekanntmachung der Einberufung zur Hauptversammlung am 24.07.2025 in Huntsville/Alabama, Vereinigte Staaten - https://central.virtualshareholdermeeting.com/vsm/web?pvske

NOTICE HEREBY IS GIVEN that the 2025 Annual Meeting of Stockholders (the "Annual Meeting") of ADTRAN Holdings, Inc. (the "Company"), which had previously been postponed, will be held on Thursday, July 24, 2025, at 11:30 a.m., Central Time, via live webcast. You can participate in the meeting by visiting https://adtran.hvanmeldung.online and entering the stockholder 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 stockholder 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 11: 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:

Stockholders will also consider and act upon such other business as may properly 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. See page 91 of the revised Proxy Statement, filed on June 6, 2025 (the “Revised Proxy Statement”) for additional details.

The Board of Directors recommends that you vote FOR each of the seven director nominees; 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, 2025. 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 Revised Proxy Statement. Stockholders of record at the close of business on May 29, 2025, are entitled to receive notice of and to vote during the Annual Meeting and any adjournments thereof. Any votes previously submitted by the Company’s stockholders in connection with the Annual Meeting will not be counted and previous proxies submitted will be disregarded, and therefore, all stockholders will need to resubmit their votes, even if they have previously voted.

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 stockholder 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 July 23, 2025 in order to be counted for the Annual Meeting unless you are voting shares of common stock held in our 401(k) plan, in which case the deadline is July 22, 2025.

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 stockholder 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.