O365 emails to *@yahoo.com all getting deferred (Error 451)

August 17, 2024

Example: I still have a dozen messages to Yahoo recepients sitting in O365 that are deferred. These were all sent without DKIM in the headers. Delivery is re-attemped every hour or so. After enabling DKIM, new messages go through on the first attempt. Old ones without DKIM stay stuck.

https://www.reddit.com/r/sysadmin/comments/1b9utjb/o365_emails_to_yahoocom_all_getting_deferred/

O365 emails to *@yahoo.com all getting deferred (Error 451) <body> <h1> Array ( [0] => i365 emails to *@yahoo.com all getting deferred (error 451) [1] => k365 emails to *@yahoo.com all getting deferred (error 451) [2] => l365 emails to *@yahoo.com all getting deferred (error 451) [3] => p365 emails to *@yahoo.com all getting deferred (error 451) [4] => 0365 emails to *@yahoo.com all getting deferred (error 451) [5] => 9365 emails to *@yahoo.com all getting deferred (error 451) [6] => o265 emails to *@yahoo.com all getting deferred (error 451) [7] => ow65 emails to *@yahoo.com all getting deferred (error 451) [8] => oe65 emails to *@yahoo.com all getting deferred (error 451) [9] => o465 emails to *@yahoo.com all getting deferred (error 451) [10] => o355 emails to *@yahoo.com all getting deferred (error 451) [11] => o3t5 emails to *@yahoo.com all getting deferred (error 451) [12] => o3y5 emails to *@yahoo.com all getting deferred (error 451) [13] => o375 emails to *@yahoo.com all getting deferred (error 451) [14] => o364 emails to *@yahoo.com all getting deferred (error 451) [15] => o36r emails to *@yahoo.com all getting deferred (error 451) [16] => o36t emails to *@yahoo.com all getting deferred (error 451) [17] => o366 emails to *@yahoo.com all getting deferred (error 451) [18] => o365 wmails to *@yahoo.com all getting deferred (error 451) [19] => o365 smails to *@yahoo.com all getting deferred (error 451) [20] => o365 dmails to *@yahoo.com all getting deferred (error 451) [21] => o365 rmails to *@yahoo.com all getting deferred (error 451) [22] => o365 4mails to *@yahoo.com all getting deferred (error 451) [23] => o365 3mails to *@yahoo.com all getting deferred (error 451) [24] => o365 enails to *@yahoo.com all getting deferred (error 451) [25] => o365 ekails to *@yahoo.com all getting deferred (error 451) [26] => o365 ejails to *@yahoo.com all getting deferred (error 451) [27] => o365 emzils to *@yahoo.com all getting deferred (error 451) [28] => o365 emsils to *@yahoo.com all getting deferred (error 451) [29] => o365 emwils to *@yahoo.com all getting deferred (error 451) [30] => o365 emqils to *@yahoo.com all getting deferred (error 451) [31] => o365 emauls to *@yahoo.com all getting deferred (error 451) [32] => o365 emajls to *@yahoo.com all getting deferred (error 451) [33] => o365 emakls to *@yahoo.com all getting deferred (error 451) [34] => o365 emaols to *@yahoo.com all getting deferred (error 451) [35] => o365 ema9ls to *@yahoo.com all getting deferred (error 451) [36] => o365 ema8ls to *@yahoo.com all getting deferred (error 451) [37] => o365 emaiks to *@yahoo.com all getting deferred (error 451) [38] => o365 emaips to *@yahoo.com all getting deferred (error 451) [39] => o365 emaios to *@yahoo.com all getting deferred (error 451) [40] => o365 emaila to *@yahoo.com all getting deferred (error 451) [41] => o365 emailz to *@yahoo.com all getting deferred (error 451) [42] => o365 emailx to *@yahoo.com all getting deferred (error 451) [43] => o365 emaild to *@yahoo.com all getting deferred (error 451) [44] => o365 emaile to *@yahoo.com all getting deferred (error 451) [45] => o365 emailw to *@yahoo.com all getting deferred (error 451) [46] => o365 emails ro *@yahoo.com all getting deferred (error 451) [47] => o365 emails fo *@yahoo.com all getting deferred (error 451) [48] => o365 emails go *@yahoo.com all getting deferred (error 451) [49] => o365 emails yo *@yahoo.com all getting deferred (error 451) [50] => o365 emails 6o *@yahoo.com all getting deferred (error 451) [51] => o365 emails 5o *@yahoo.com all getting deferred (error 451) [52] => o365 emails ti *@yahoo.com all getting deferred (error 451) [53] => o365 emails tk *@yahoo.com all getting deferred (error 451) [54] => o365 emails tl *@yahoo.com all getting deferred (error 451) [55] => o365 emails tp *@yahoo.com all getting deferred (error 451) [56] => o365 emails t0 *@yahoo.com all getting deferred (error 451) [57] => o365 emails t9 *@yahoo.com all getting deferred (error 451) [58] => o365 emails to *@tahoo.com all getting deferred (error 451) [59] => o365 emails to *@gahoo.com all getting deferred (error 451) [60] => o365 emails to *@hahoo.com all getting deferred (error 451) [61] => o365 emails to *@uahoo.com all getting deferred (error 451) [62] => o365 emails to *@7ahoo.com all getting deferred (error 451) [63] => o365 emails to *@6ahoo.com all getting deferred (error 451) [64] => o365 emails to *@yzhoo.com all getting deferred (error 451) [65] => o365 emails to *@yshoo.com all getting deferred (error 451) [66] => o365 emails to *@ywhoo.com all getting deferred (error 451) [67] => o365 emails to *@yqhoo.com all getting deferred (error 451) [68] => o365 emails to *@yagoo.com all getting deferred (error 451) [69] => o365 emails to *@yaboo.com all getting deferred (error 451) [70] => o365 emails to *@yanoo.com all getting deferred (error 451) [71] => o365 emails to *@yajoo.com all getting deferred (error 451) [72] => o365 emails to *@yauoo.com all getting deferred (error 451) [73] => o365 emails to *@yayoo.com all getting deferred (error 451) [74] => o365 emails to *@yahio.com all getting deferred (error 451) [75] => o365 emails to *@yahko.com all getting deferred (error 451) [76] => o365 emails to *@yahlo.com all getting deferred (error 451) [77] => o365 emails to *@yahpo.com all getting deferred (error 451) [78] => o365 emails to *@yah0o.com all getting deferred (error 451) [79] => o365 emails to *@yah9o.com all getting deferred (error 451) [80] => o365 emails to *@yahoi.com all getting deferred (error 451) [81] => o365 emails to *@yahok.com all getting deferred (error 451) [82] => o365 emails to *@yahol.com all getting deferred (error 451) [83] => o365 emails to *@yahop.com all getting deferred (error 451) [84] => o365 emails to *@yaho0.com all getting deferred (error 451) [85] => o365 emails to *@yaho9.com all getting deferred (error 451) [86] => o365 emails to *@yahoo,com all getting deferred (error 451) [87] => o365 emails to *@yahoolcom all getting deferred (error 451) [88] => o365 emails to *@yahoo;com all getting deferred (error 451) [89] => o365 emails to *@yahoo/com all getting deferred (error 451) [90] => o365 emails to *@yahoo.xom all getting deferred (error 451) [91] => o365 emails to *@yahoo.vom all getting deferred (error 451) [92] => o365 emails to *@yahoo.fom all getting deferred (error 451) [93] => o365 emails to *@yahoo.dom all getting deferred (error 451) [94] => o365 emails to *@yahoo.cim all getting deferred (error 451) [95] => o365 emails to *@yahoo.ckm all getting deferred (error 451) [96] => o365 emails to *@yahoo.clm all getting deferred (error 451) [97] => o365 emails to *@yahoo.cpm all getting deferred (error 451) [98] => o365 emails to *@yahoo.c0m all getting deferred (error 451) [99] => o365 emails to *@yahoo.c9m all getting deferred (error 451) [100] => o365 emails to *@yahoo.con all getting deferred (error 451) [101] => o365 emails to *@yahoo.cok all getting deferred (error 451) [102] => o365 emails to *@yahoo.coj all getting deferred (error 451) [103] => o365 emails to *@yahoo.com zll getting deferred (error 451) [104] => o365 emails to *@yahoo.com sll getting deferred (error 451) [105] => o365 emails to *@yahoo.com wll getting deferred (error 451) [106] => o365 emails to *@yahoo.com qll getting deferred (error 451) [107] => o365 emails to *@yahoo.com akl getting deferred (error 451) [108] => o365 emails to *@yahoo.com apl getting deferred (error 451) [109] => o365 emails to *@yahoo.com aol getting deferred (error 451) [110] => o365 emails to *@yahoo.com alk getting deferred (error 451) [111] => o365 emails to *@yahoo.com alp getting deferred (error 451) [112] => o365 emails to *@yahoo.com alo getting deferred (error 451) [113] => o365 emails to *@yahoo.com all fetting deferred (error 451) [114] => o365 emails to *@yahoo.com all vetting deferred (error 451) [115] => o365 emails to *@yahoo.com all betting deferred (error 451) [116] => o365 emails to *@yahoo.com all hetting deferred (error 451) [117] => o365 emails to *@yahoo.com all yetting deferred (error 451) [118] => o365 emails to *@yahoo.com all tetting deferred (error 451) [119] => o365 emails to *@yahoo.com all gwtting deferred (error 451) [120] => o365 emails to *@yahoo.com all gstting deferred (error 451) [121] => o365 emails to *@yahoo.com all gdtting deferred (error 451) [122] => o365 emails to *@yahoo.com all grtting deferred (error 451) [123] => o365 emails to *@yahoo.com all g4tting deferred (error 451) [124] => o365 emails to *@yahoo.com all g3tting deferred (error 451) [125] => o365 emails to *@yahoo.com all gerting deferred (error 451) [126] => o365 emails to *@yahoo.com all gefting deferred (error 451) [127] => o365 emails to *@yahoo.com all gegting deferred (error 451) [128] => o365 emails to *@yahoo.com all geyting deferred (error 451) [129] => o365 emails to *@yahoo.com all ge6ting deferred (error 451) [130] => o365 emails to *@yahoo.com all ge5ting deferred (error 451) [131] => o365 emails to *@yahoo.com all getring deferred (error 451) [132] => o365 emails to *@yahoo.com all getfing deferred (error 451) [133] => o365 emails to *@yahoo.com all getging deferred (error 451) [134] => o365 emails to *@yahoo.com all getying deferred (error 451) [135] => o365 emails to *@yahoo.com all get6ing deferred (error 451) [136] => o365 emails to *@yahoo.com all get5ing deferred (error 451) [137] => o365 emails to *@yahoo.com all gettung deferred (error 451) [138] => o365 emails to *@yahoo.com all gettjng deferred (error 451) [139] => o365 emails to *@yahoo.com all gettkng deferred (error 451) [140] => o365 emails to *@yahoo.com all gettong deferred (error 451) [141] => o365 emails to *@yahoo.com all gett9ng deferred (error 451) [142] => o365 emails to *@yahoo.com all gett8ng deferred (error 451) [143] => o365 emails to *@yahoo.com all gettibg deferred (error 451) [144] => o365 emails to *@yahoo.com all gettimg deferred (error 451) [145] => o365 emails to *@yahoo.com all gettijg deferred (error 451) [146] => o365 emails to *@yahoo.com all gettihg deferred (error 451) [147] => o365 emails to *@yahoo.com all gettinf deferred (error 451) [148] => o365 emails to *@yahoo.com all gettinv deferred (error 451) [149] => o365 emails to *@yahoo.com all gettinb deferred (error 451) [150] => o365 emails to *@yahoo.com all gettinh deferred (error 451) [151] => o365 emails to *@yahoo.com all gettiny deferred (error 451) [152] => o365 emails to *@yahoo.com all gettint deferred (error 451) [153] => o365 emails to *@yahoo.com all getting seferred (error 451) [154] => o365 emails to *@yahoo.com all getting xeferred (error 451) [155] => o365 emails to *@yahoo.com all getting ceferred (error 451) [156] => o365 emails to *@yahoo.com all getting feferred (error 451) [157] => o365 emails to *@yahoo.com all getting referred (error 451) [158] => o365 emails to *@yahoo.com all getting eeferred (error 451) [159] => o365 emails to *@yahoo.com all getting dwferred (error 451) [160] => o365 emails to *@yahoo.com all getting dsferred (error 451) [161] => o365 emails to *@yahoo.com all getting ddferred (error 451) [162] => o365 emails to *@yahoo.com all getting drferred (error 451) [163] => o365 emails to *@yahoo.com all getting d4ferred (error 451) [164] => o365 emails to *@yahoo.com all getting d3ferred (error 451) [165] => o365 emails to *@yahoo.com all getting dederred (error 451) [166] => o365 emails to *@yahoo.com all getting decerred (error 451) [167] => o365 emails to *@yahoo.com all getting deverred (error 451) [168] => o365 emails to *@yahoo.com all getting degerred (error 451) [169] => o365 emails to *@yahoo.com all getting deterred (error 451) [170] => o365 emails to *@yahoo.com all getting dererred (error 451) [171] => o365 emails to *@yahoo.com all getting defwrred (error 451) [172] => o365 emails to *@yahoo.com all getting defsrred (error 451) [173] => o365 emails to *@yahoo.com all getting defdrred (error 451) [174] => o365 emails to *@yahoo.com all getting defrrred (error 451) [175] => o365 emails to *@yahoo.com all getting def4rred (error 451) [176] => o365 emails to *@yahoo.com all getting def3rred (error 451) [177] => o365 emails to *@yahoo.com all getting defeered (error 451) [178] => o365 emails to *@yahoo.com all getting defedred (error 451) [179] => o365 emails to *@yahoo.com all getting defefred (error 451) [180] => o365 emails to *@yahoo.com all getting defetred (error 451) [181] => o365 emails to *@yahoo.com all getting defe5red (error 451) [182] => o365 emails to *@yahoo.com all getting defe4red (error 451) [183] => o365 emails to *@yahoo.com all getting defereed (error 451) [184] => o365 emails to *@yahoo.com all getting deferded (error 451) [185] => o365 emails to *@yahoo.com all getting deferfed (error 451) [186] => o365 emails to *@yahoo.com all getting deferted (error 451) [187] => o365 emails to *@yahoo.com all getting defer5ed (error 451) [188] => o365 emails to *@yahoo.com all getting defer4ed (error 451) [189] => o365 emails to *@yahoo.com all getting deferrwd (error 451) [190] => o365 emails to *@yahoo.com all getting deferrsd (error 451) [191] => o365 emails to *@yahoo.com all getting deferrdd (error 451) [192] => o365 emails to *@yahoo.com all getting deferrrd (error 451) [193] => o365 emails to *@yahoo.com all getting deferr4d (error 451) [194] => o365 emails to *@yahoo.com all getting deferr3d (error 451) [195] => o365 emails to *@yahoo.com all getting deferres (error 451) [196] => o365 emails to *@yahoo.com all getting deferrex (error 451) [197] => o365 emails to *@yahoo.com all getting deferrec (error 451) [198] => o365 emails to *@yahoo.com all getting deferref (error 451) [199] => o365 emails to *@yahoo.com all getting deferrer (error 451) [200] => o365 emails to *@yahoo.com all getting deferree (error 451) [201] => o365 emails to *@yahoo.com all getting deferred (wrror 451) [202] => o365 emails to *@yahoo.com all getting deferred (srror 451) [203] => o365 emails to *@yahoo.com all getting deferred (drror 451) [204] => o365 emails to *@yahoo.com all getting deferred (rrror 451) [205] => o365 emails to *@yahoo.com all getting deferred (4rror 451) [206] => o365 emails to *@yahoo.com all getting deferred (3rror 451) [207] => o365 emails to *@yahoo.com all getting deferred (eeror 451) [208] => o365 emails to *@yahoo.com all getting deferred (edror 451) [209] => o365 emails to *@yahoo.com all getting deferred (efror 451) [210] => o365 emails to *@yahoo.com all getting deferred (etror 451) [211] => o365 emails to *@yahoo.com all getting deferred (e5ror 451) [212] => o365 emails to *@yahoo.com all getting deferred (e4ror 451) [213] => o365 emails to *@yahoo.com all getting deferred (ereor 451) [214] => o365 emails to *@yahoo.com all getting deferred (erdor 451) [215] => o365 emails to *@yahoo.com all getting deferred (erfor 451) [216] => o365 emails to *@yahoo.com all getting deferred (ertor 451) [217] => o365 emails to *@yahoo.com all getting deferred (er5or 451) [218] => o365 emails to *@yahoo.com all getting deferred (er4or 451) [219] => o365 emails to *@yahoo.com all getting deferred (errir 451) [220] => o365 emails to *@yahoo.com all getting deferred (errkr 451) [221] => o365 emails to *@yahoo.com all getting deferred (errlr 451) [222] => o365 emails to *@yahoo.com all getting deferred (errpr 451) [223] => o365 emails to *@yahoo.com all getting deferred (err0r 451) [224] => o365 emails to *@yahoo.com all getting deferred (err9r 451) [225] => o365 emails to *@yahoo.com all getting deferred (erroe 451) [226] => o365 emails to *@yahoo.com all getting deferred (errod 451) [227] => o365 emails to *@yahoo.com all getting deferred (errof 451) [228] => o365 emails to *@yahoo.com all getting deferred (errot 451) [229] => o365 emails to *@yahoo.com all getting deferred (erro5 451) [230] => o365 emails to *@yahoo.com all getting deferred (erro4 451) [231] => o365 emails to *@yahoo.com all getting deferred (error 351) [232] => o365 emails to *@yahoo.com all getting deferred (error e51) [233] => o365 emails to *@yahoo.com all getting deferred (error r51) [234] => o365 emails to *@yahoo.com all getting deferred (error 551) [235] => o365 emails to *@yahoo.com all getting deferred (error 441) [236] => o365 emails to *@yahoo.com all getting deferred (error 4r1) [237] => o365 emails to *@yahoo.com all getting deferred (error 4t1) [238] => o365 emails to *@yahoo.com all getting deferred (error 461) [239] => o365 emails to *@yahoo.com all getting deferred (error 452) [240] => o365 emails to *@yahoo.com all getting deferred (error 45q) ) </h1> </body>