(Bloomberg) -- A controversial mailbox outside an Amazon.com Inc. warehouse during a recent union election was modified by the U.S. Postal Service after a senior executive supported its installation, according to testimony at a hearing over the disputed vote.A USPS official told the hearing Monday that agency personnel removed a divider normally placed between the outgoing mail slot and the parcel slot. Photos displayed during the hearing also showed another missing divider that could potentially let someone collecting letters access outbound mail as well. The revelations followed testimony last week from an Amazon employee who said he saw company security guards use a key to open one of the mail boxes.The mailbox outside Amazon’s Bessemer, Alabama, facility is at the center of the Retail, Wholesale and Department Store Union’s bid to overturn its election loss there. Amazon says it requested the mailbox to provide a secure and convenient means for employees to vote, but the union says the mailbox gave Amazon the ability to spy on workers as they voted and created the appearance that the retail giant was involved in conducting the election.The National Labor Relations Board, which oversees union votes, started holding hearings last week on the RWDSU’s objections. Emails displayed during the Zoom hearing on Monday detailed the extent of Amazon’s campaign, which looped in senior USPS officials in Washington. In one email, an Amazon official said the mailbox’s installation was a top priority for senior leadership, including retail and logistics chief Dave Clark.“Please let me know where we stand on this -- this is a highly visible Dave Clark initiative,” Becky Moore, a senior manager at Amazon, wrote to USPS officials in late January, seeking an update on the company’s request. Another email indicated that Adam Baker, a vice president with Amazon’s transportation group, had “escalated” the request to Jacqueline Krage Strako, USPS’s chief commerce and business solutions officer, who reports to Postmaster General Louis DeJoy.Jay Smith, director of enterprise and key accounts for the USPS, testified on Monday that the postal service had determined it could not place a blue collection box outside the warehouse on a temporary basis. Instead, it decided to install a cluster box, a rectangular steel enclosure that contains multiple locked doors, a setup often found at apartment complexes or commercial buildings. Smith said it was the first time he was aware of USPS installing a cluster box at the request of a private customer.In early February, Smith informed Moore and Brian Palmer, a senior manager with Amazon’s public policy group in Washington, that USPS would install a cluster box outside the facility later that week. (Portions of the email exchanges, some of which were obtained in redacted form by the union through Freedom of Information Act requests, were reported last month by the Washington Post.)The cluster box appears from the outside to be divided into 14 compartments -- 12 numbered mailboxes for different recipients’ incoming mail, a compartment for outgoing mail and a larger compartment at the bottom right, normally used for parcels, labeled “1P.” Amazon employee Kevin Jackson testified last week that he saw the security guards open the box labeled “1P.”Smith said the divider between the outgoing mail slot and the parcel slot was removed to create more room for ballots.But images of the mailbox with all of its doors ajar shown during Monday’s hearing also appeared to indicate another modification: no divider between mailbox 12 and the outgoing mail compartment. According to the photos, a mail recipient who possessed a key to box 12 may have been able to access outgoing mail as well.During cross-examination by a lawyer representing Amazon, Smith said the company was not given a copy of the “arrow key” necessary to open the outgoing mail compartment, a key to the parcel box, or a key to box no. 12 for the purposes of accessing outgoing mail. Any effort to allow the company access to the compartment would have violated agency policy, he said.Smith did say that Amazon, as an addressee at the site, would have had keys to open whichever of the recipient mailboxes that it was assigned. It is unclear which box Amazon used. Smith said the installation of the cluster box, which had previously sat unused, was within postal service policy.Palmer subsequently asked Smith if it would be all right to place a “vote here” sticker above the outgoing mail slot, according to an email presented on Monday. Smith testified that he told Amazon it wasn’t possible. He added that he was surprised to learn, from images published in the Washington Post, that Amazon had erected a tent over the mailbox bearing the text “Speak for yourself! Mail your ballot here.”“I did not want to see anything else put around that box indicating that it was a vote,” Smith said.(Updates with details to mailbox modifications beginning in the first paragraph.)For more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2021 Bloomberg L.P.