Double-bounce Suppression of 'Recipient address rejected'

DSNs sent on behalf of the Customer for "Recipient address rejected: User unknown in local recipient table" at the Customer Side while directed to double-bounce@mx1.mxguard.uk are still being received by Customers. For example, today, mail to the following, non-existent, local recipients resulted in a connection from mx1.mxguard.uk to the Customer attempting to deliver a DSN to the Customer's invalid local addresses: 2026-05-24T09:31 pr5gomee 2026-05-24T10:04 03mooo 2026-05-24T10:42 bb 2026-05-24T12:07 a1aaa1azzzz1zaaaaa 2026-05-24T12:32 bb 2026-05-24T13:23 carys 2026-05-24T13:28 j.tri5g16r 2026-05-24T13:37 tet 2026-05-24T16:08 carys 2026-05-24T16:29 dsw 2026-05-24T16:53 j.tri5g16r 2026-05-24T16:56 in 2026-05-24T17:01 stevenm 2026-05-24T17:38 l.nk7mmlq0dqf 2026-05-24T18:23 tet 2026-05-24T20:32 carys 2026-05-24T23:18 dsw 2026-05-25T04:27 stephenm 2026-05-25T04:47 stevenm 2026-05-25T04:53 zbnshkhcmz.lfhfgkzpmg 2026-05-25T05:01 in 2026-05-25T12:55 a1aaa1azzzz1zaaaaa 2026-05-25T15:13 bb 2026-05-25T15:18 03mooo 2026-05-25T15:28 l.nk7mmlq0dqf 2026-05-25T15:43 dsw 2026-05-25T16:07 carys 2026-05-25T17:15 carys 2026-05-25T17:26 dsw 2026-05-25T18:11 pr5gomee 2026-05-25T18:15 tet 2026-05-25T19:58 carys 2026-05-25T20:56 j.tri5g16r 2026-05-25T21:19 in 2026-05-25T21:31 carys 2026-05-26T00:32 tet 2026-05-26T04:38 stevenm 2026-05-26T11:20 j.tri5g16r 2026-05-26T11:44 pr5gomee 2026-05-26T12:21 a1aaa1azzzz1zaaaaa 2026-05-26T12:31 in 2026-05-26T12:46 pr5gomee 2026-05-26T12:58 tet 2026-05-26T13:09 03mooo 2026-05-26T13:55 bb 2026-05-26T14:08 carys 2026-05-26T14:09 stevenm 2026-05-26T14:19 dsw 2026-05-26T15:13 l.nk7mmlq0dqf 2026-05-26T15:27 dsw Obviously some of these recur (e.g. bb, carys, dsw)