[425] SYNOVUS FINANCIAL CORP Business Combination Communication

Filed by Synovus Financial Corp.

pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-6

under the Securities Exchange Act of 1934

Subject Company: Steel Newco Inc.

Commission File No.: 333-289866

Date: October 17, 2025

[The following letter was mailed to certain shareholders of Synovus Financial Corp.]

October 17, 2025

Dear Fellow Shareholder:

According to our latest records, we have not yet received your vote with respect to the important special meeting of holders of Synovus common stock to be held on November 6, 2025, in connection with the proposed merger with Pinnacle Financial Partners, Inc. (the “Merger”). Remember, failing to vote will have the same effect as a vote against the Merger; therefore your vote is very important, regardless of the number of shares you own.

Your Board of Directors unanimously recommends that you vote FOR the Merger and related proposals.

To ensure your shares are represented, please take a moment to vote TODAY, via the Internet, by telephone, or by signing, dating, and returning the enclosed proxy card or voting instruction form in the envelope provided.

On behalf of Synovus Financial Corp., thank you for your support.

Sincerely,

/s/ Kevin Blair

Kevin Blair

Chairman, Chief Executive Officer and President

REMEMBER:

You can vote your shares online or by phone—it’s simple and quick.

Please follow the easy instructions on the enclosed proxy card or voting instruction form.

If you have any questions, or need assistance in voting your shares, please call our proxy solicitor:

INNISFREE M&A INCORPORATED

1 (877) 456-3524 (toll-free from the U.S. and Canada) or

+1 (412) 232-3651 (from other countries)

Important Information About the Merger and Where to Find It

Steel Newco Inc. (“Newco”) filed a registration statement on Form S-4 (File No. 333-289866) with the SEC on August 26, 2025, and an amendment on September 29, 2025, to register the shares of Newco common stock that will be issued to Pinnacle shareholders and Synovus shareholders in connection with the proposed transaction. The registration statement includes a joint proxy statement of Synovus and Pinnacle that also constitutes a prospectus of Newco. The registration statement was declared effective on September 30, 2025. Newco filed a prospectus on September 30, 2025, and Synovus and Pinnacle each filed a definitive proxy statement on September 30, 2025. Synovus and Pinnacle each commenced mailing of the definitive joint proxy statement/prospectus to their respective shareholders on or about September 30, 2025. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT AND DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS (AND ANY OTHER DOCUMENTS THAT HAVE BEEN OR MAY BE FILED WITH THE SEC IN CONNECTION WITH THE TRANSACTION OR INCORPORATED BY REFERENCE INTO THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS) BECAUSE SUCH DOCUMENTS WILL CONTAIN IMPORTANT INFORMATION REGARDING THE PROPOSED TRANSACTION AND RELATED MATTERS. Investors and security holders may obtain free copies of these documents and other documents filed with the SEC by Synovus, Pinnacle or Newco through the website maintained by the SEC at http://www.sec.gov or by contacting the investor relations department of Synovus or Pinnacle at:

Synovus Financial Corp.	Pinnacle Financial Partners, Inc.
33 West 14th Street	21 Platform Way South
Columbus, GA 31901	Nashville, TN 37203
Attention: Investor Relations	Attention: Investor Relations
InvestorRelations@Synovus.com	Investor.Relations@pnfp.com
(706) 641-6500	(615) 743-8219

Before making any voting or investment decision, investors and security holders of Synovus and Pinnacle are urged to read carefully the entire registration statement and definitive joint proxy statement/prospectus, including any amendments thereto, because they contain important information about the proposed transaction. Free copies of these documents may be obtained as described above.

Participants in Solicitation

Synovus and Pinnacle and their respective directors and executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies from Synovus’ shareholders and Pinnacle’s shareholders in respect of the proposed transaction under the rules of the SEC. Information regarding Synovus’ directors and executive officers is available in Synovus’ proxy statement for its 2025 annual meeting of shareholders, filed with the SEC on March 12, 2025 (and available at https://www.sec.gov/ix?doc=/Archives/edgar/data/0000018349/000001834925000057/syn-20250312.htm) (the “Synovus 2025 Proxy”), under the headings “Corporate Governance and Board Matters,” “Director Compensation,” “Proposal 1 Election of Directors,” “Executive Officers,” “Stock Ownership of Directors and Named Executive Officers,” “Executive Compensation,” “Compensation and Human Capital Committee Report,” “Summary Compensation Table,” and “Certain Relationships and Related Transactions,” and in Synovus’ Annual Report on Form 10-K for the year ended December 31, 2024, filed with the SEC on February 21, 2025 (and available at https://www.sec.gov/ix?doc=/Archives/edgar/data/0000018349/000001834925000049/syn-20241231.htm), and in other documents subsequently filed by Synovus with the SEC, which can be obtained free of charge through the website maintained by the SEC at http://www.sec.gov. Any changes in the holdings of Synovus’ securities by Synovus’ directors or executive officers from the amounts described in the Synovus 2025 Proxy have been or will be reflected on Initial Statements of Beneficial Ownership of Securities on Form 3 or on Statements of Change in Ownership on Form 4 filed with the SEC subsequent to the filing date of the Synovus 2025 Proxy and are available at the SEC’s website at www.sec.gov. Information regarding Pinnacle’s directors and executive officers is available in Pinnacle’s proxy statement for its 2025 annual meeting of shareholders, filed with the SEC on March 3, 2025 (and available at https://www.sec.gov/ix?doc=/Archives/edgar/data/1115055/000111505525000063/pnfp-20250303.htm) (the “Pinnacle 2025 Proxy”), under the headings “Environmental, Social and Corporate Governance,” “Proposal 1 Election of Directors,” “Information About Our Executive Officers,” “Executive Compensation,” “Security Ownership of Certain Beneficial Owners and Management,” and “Certain Relationships and Related Transactions,” and in Pinnacle’s Annual Report on Form 10-K for the year ended December 31, 2024, filed with the SEC on February 25, 2025 (and available at https://www.sec.gov/ix?doc=/Archives/edgar/data/1115055/000111505525000042/pnfp-20241231.htm), and in other documents subsequently filed by Pinnacle with the SEC, which can be obtained free of charge through the website maintained by the SEC at http://www.sec.gov. Any changes in the holdings of Pinnacle’s securities by Pinnacle’s directors or executive officers from the amounts described in the Pinnacle 2025 Proxy have been or will be reflected on Initial Statements of Beneficial Ownership of Securities on Form 3 or on Statements of Change in Ownership on Form 4 filed with the SEC subsequent to the filing date of the Pinnacle 2025 Proxy and are available at the SEC’s website at www.sec.gov. Additional information regarding the interests of such participants is included in the definitive joint proxy statement/prospectus and will be included in other relevant materials to be filed with the SEC.

No Offer or Solicitation

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.