Some mail servers (MX hosts) have associated TLSA records with certificate usage 2 (DANE-TA) that match one of the retired Let's Encrypt issuer CAs. The retired CAs include:
All certificates issued by the "X1", "X2", "X3" and "X4" intermediate issuing CAs to DANE MX hosts have long ago expired. As of 2024-09-03, so have those issued by the "R3", "R4", "E1" or "E2" issuing CAs.
When you do publish TLSA records matching a Let's Encrypt issuing CA, make sure to publish the full set of records for ALL the related CAs:
For "R10" or "R11", include both, and their backups R12–R14.
For "E5" or "E6", include both, and their backups E7–E9.
For the "ISRG Root X1" or "ISRG Root X2" trust anchors, include both (see additional requirements for TLSA records matching root CAs below).
All Let's Encrypt users publishing DANE-TA(2) TLSA records need to update their TLSA records to publish records that match the intermediate issuer CAs that issued their current certificate and to pre-publish records for upcoming CAs if the current issuer is no longer active.
If your server's private and public keys are RSA keys, you can publish TLSA records matching just the "R*" CA public keys, and with ECDSA keys, just the "E*" CA public keys. If your server has both RSA and ECDSA keys, you'll need to publish TLSA records matching both the "R*" and "E*" issuer CAs. You can't rely on certificate renewal always using the same intermediate CA as before, or that the backup issuers might not be used instead. Therefore, list all "R*" and/or "E*" records. See the tables below for details.
Thus, SMTP server operators using DANE-TA(2) with Let's Encrypt certificates must publish the applicable groups of TLSA records from the below (possibly in addition to "3 1 1" records matching the server public key) for each of their MX hosts in order to prevent delivery failures.
| CA tag | Active RSA issuer CAs |
|---|---|
| R10 | _25._tcp.each.mx.host. IN TLSA 2 1 1 2bbad93ab5c79279ec121507f272cbe0c6647a3aae52e22f388afab426b4adba |
| R11 | _25._tcp.each.mx.host. IN TLSA 2 1 1 6ddac18698f7f1f7e1c69b9bce420d974ac6f94ca8b2c761701623f99c767dc7 |
| R12 | _25._tcp.each.mx.host. IN TLSA 2 1 1 919c0df7a787b597ed056ace654b1de9c0387acf349f73734a4fd7b58cf612a4 |
| R13 | _25._tcp.each.mx.host. IN TLSA 2 1 1 025490860b498ab73c6a12f27a49ad5fe230fafe3ac8f6112c9b7d0aad46941d |
| R14 | _25._tcp.each.mx.host. IN TLSA 2 1 1 f1647a5ee3efac54c892e930584fe47979b7acd1c76c1271bca1c5076d869888 |
| CA tag | Active ECDSA issuer CAs |
|---|---|
| E5 | _25._tcp.each.mx.host. IN TLSA 2 1 1 3586d4ecf070578cbd27aedce20b964e48bc149faeb9dad72f46b857869172b8 |
| E6 | _25._tcp.each.mx.host. IN TLSA 2 1 1 d016e1fe311948aca64f2de44ce86c9a51ca041df6103bb52a88eb3f761f57d7 |
| E7 | _25._tcp.each.mx.host. IN TLSA 2 1 1 cbbc559b44d524d6a132bdac672744da3407f12aae5d5f722c5f6c7913871c75 |
| E8 | _25._tcp.each.mx.host. IN TLSA 2 1 1 885bf0572252c6741dc9a52f5044487fef2a93b811cdedfad7624cc283b7cdd5 |
| E9 | _25._tcp.each.mx.host. IN TLSA 2 1 1 f1440a9b76e1e41e53a4cb461329bf6337b419726be513e42e19f1c691c5d4b2 |
Any other "2 1 1" records that were once associated with Let's Encrypt SHOULD NOT be used. They can't possibly match an unexpired certificate, and are just bloat in DNS TLSA lookup results, and an unnecessary security risk (if the obsolete keys are compromised). These include:
| CA tag | Retired issuer CAs to avoid |
|---|---|
| X1/X3 | _25._tcp.each.mx.host. IN TLSA 2 1 1 60b87575447dcba2a36b7d11ac09fb24a9db406fee12d2cc90180517616e8a18 |
| X2/X4 | _25._tcp.each.mx.host. IN TLSA 2 1 1 b111dd8a1c2091a89bd4fd60c57f0716cce50feeff8137cdbee0326e02cf362b |
| R3 | _25._tcp.each.mx.host. IN TLSA 2 1 1 8d02536c887482bc34ff54e41d2ba659bf85b341a0a20afadb5813dcfbcf286d |
| R4 | _25._tcp.each.mx.host. IN TLSA 2 1 1 e5545e211347241891c554a03934cde9b749664a59d26d615fe58f77990f2d03 |
| E1 | _25._tcp.each.mx.host. IN TLSA 2 1 1 276fe8a8c4ec7611565bf9fce6dcace9be320c1b5bea27596b2204071ed04f10 |
| E2 | _25._tcp.each.mx.host. IN TLSA 2 1 1 bd936e72b212ef6f773102c6b77d38f94297322efc25396bc3279422e0c89270 |
For the Let's Encrypt CAs, please also avoid all TLSA parameter combinations other than "2 1 1", with an associated SHA2-256 digest of the CA public key (not the full certificate).
MX hosts whose TLSA records include only inactive CA key digests are no longer able to receive email from sending systems that perform DANE validation.
With a bit of care, one can instead publish TLSA records matching one of the "ISRG X1" or "ISRG X2" root CAs, but one then has to carefully ensure that the root CA certificates are appended to the server's chain file (not the case with chain files produced by, e.g., certbot), so the ACME chain file may require post-processing before it is configured as the MTA's certificate chain. The root CA public key hashes are:
| CA tag | ISRG Root CAs |
|---|---|
| ISRG X1 | _25._tcp.each.mx.host. IN TLSA 2 1 1 0b9fa5a59eed715c26c1020c711b4f6ec42d58b0015e14337a39dad301c5afc3 |
| ISRG X2 | _25._tcp.each.mx.host. IN TLSA 2 1 1 762195c225586ee6c0237456e2107dc54f1efc21f61a792ebd515913cce68332 |
Of course even the above root CA TLSA records are not safe to then indefinitely ignore, the roots are also subject to occasional bitrot. Only the "3 1 1" records matching your server's public keys are under your control and change only when *you* decide to switch to new keys.
Hence, my best advice is to not play Let's Encrypt whack-a-mole, and use "3 1 1" records with stable keys (not automatically replaced with every renewal). You should choose when to rekey, and prepublish matching TLSA records before you do so. You may find danebot or similar tools helpful.
Finally, please avoid issuer TLSA records with selector Cert(0), i.e. "2 0 1" and "2 0 2". These are much more fragile, for example, some of the "E*" certificates will be issued by the RSA "X1" root, while others by the newer ECDSA "X2" root.
The table below lists MX hosts that are still publishing TLSA records matching the retired "X1", "X2", "X3", "X4", "R3", "R4", "E1" or "E2" CAs as well as the outdated R3 or R4 cross-certificates issued by DST. It is sorted to list hosts that serve the most domains first.
| signed domains | host name |
|---|---|
| 15923 | mx1.vevida.com |
| 15919 | mx3.vevida.com |
| 15918 | mx2.vevida.com |
| 15912 | mx4.vevida.com |
| 15907 | backup-mx.vevida.com |
| 9925 | mail.wido.info |
| 7735 | mx1.simplelogin.co |
| 7730 | mx2.simplelogin.co |
| 584 | mail.srvfarm.net |
| 246 | smtp1.protagio.nl |
| 245 | smtp2.protagio.nl |
| 62 | polina.gro.momou.ch |
| 62 | polina.lan11.momou.ch |
| 60 | polina.duc.momou.ch |
| 60 | mail.tmkis.com |
| 58 | mail.netfuture.ch |
| 56 | ecn3.ecn.cz |
| 54 | mx2.amsterdamtech.net |
| 51 | ecn4.ecn.cz |
| 38 | merlin.cutisan.dk |
| 34 | mx2.ernstberger.cloud |
| 33 | mail.drk-rhn.de |
| 29 | mail.machineitservices.com |
| 28 | hosting01.spotler.net |
| 22 | web2.sys.ccs-baumann.de |
| 22 | mx1.mxspamfilter.de |
| 22 | web1.sys.ccs-baumann.de |
| 21 | mx2.mxspamfilter.de |
| 21 | smtp.muehlberger.net |
| 20 | in4smtp.std-service.com |
| 20 | altair.ne2000.nl |
| 20 | castor.ne2000.nl |
| 19 | smtp.std-service.com |
| 19 | mx2.mchosted.nl |
| 18 | backup-mx.muehlberger.net |
| 18 | smtp.astrath.net |
| 17 | hosting03.spotler.net |
| 16 | mx1.lspd.net |
| 15 | artemis.strebsjig.net |
| 14 | lightning.heliumnet.nl |
| 14 | mail-ec2.moving-target.info |
| 14 | hailstone.heliumnet.nl |
| 14 | mailcow.wewitro.net |
| 13 | mx02.o-o-s.de |
| 12 | hg.net2service.com |
| 12 | lcars.douzer.de |
| 12 | mail.twe.net |
| 12 | caladan.freestone.net |
| 12 | autonomy.gwynethllewelyn.net |
| 12 | ncars.douzer.de |
| 11 | mail.ideas-in-logic.de |
| 11 | mail.raven.express |
| 10 | mx3.vforge.net |
| 10 | mx.spodhuis.org |
| 10 | mail.yzal.io |
| 10 | mail.herenstraat.nl |
| 10 | mail.sportvereine.online |
| 10 | mx1.vforge.net |
| 10 | mx2.vforge.net |
| 9 | transfer.abstractsupports.au |
| 9 | dispatch.abstractsupports.au |
| 9 | mail.argantiu.de |
| 9 | mail.js86.de |
| 9 | mail.jeatranslations.nl |
| 9 | mail.chas.se |
| 9 | conveyor.abstractsupports.au |
| 8 | truncheon.ain.net |
| 8 | mx1.mailserver.ovh |
| 8 | any.qu1x.one |
| 7 | mail.asda.gr |
| 7 | mx2.asda.gr |
| 7 | hitch.fr |
| 7 | server.ist-immer-online.de |
| 7 | mail.d9ping.nl |
| 7 | mail.evangineer.net |
| 7 | mail.jth.net |
| 7 | bovender.de |
| 7 | ibio.nl |
| 7 | mail.neef-media.com |
| 7 | cloud.michaonline.net |
| 7 | mailbackup.d9ping.nl |
| 7 | ra.horus-it.com |
| 6 | mail.kurim.de |
| 6 | mail.bludesio.eu |
| 6 | smtp-in.goedel.dlitz.net |
| 6 | mail.ffct.eu |
| 6 | mx.squareip.nl |
| 6 | mx2.lspd.net |
| 6 | mx01.mindorf-online.de |
| 6 | mail.spookje.org |
| 6 | smtp.koeroo.net |
| 6 | mailgw.itsecf.de |
| 6 | mail.connies-diner.de |
| 6 | dev.koan19.net |
| 6 | mail.schem.me |
| 6 | mail.w4w.de |
| 6 | eurekamaru.vrhein.de |
| 5 | torte.teemitmil.ch |
| 5 | mx1.ironie.org |
| 5 | mx2.ironie.org |
| 5 | applejack.mvld.eu |
| 5 | mail.mxgateway.eu |
| 5 | mx1.nerdpol.org |
| 5 | sys1.mmini.de |
| 5 | mail.newday.host |
| 5 | mailserver.adrian2023.com |
| 5 | mail.no-uce.de |
| 5 | srv002.osdbrw.de |
| 5 | mail.blep.cz |
| 5 | mx.xserownia.net |
| 5 | smtp.maths.network |
| 5 | mail.rs-netzwerk.de |
| 5 | mx1.darvo.nl |
| 5 | mail.seelentium.de |
| 5 | insblauehinein.nl |
| 5 | box2.tolerantnetworks.com |
| 5 | mc.ulischaefer.de |
| 5 | mx.boesger.de |
| 5 | postbox.idefix.net |
| 5 | mxb.boesger.de |
| 5 | mail.aegrel.ee |
| 4 | smtp.hs-bund.de |
| 4 | mail.servut.org |
| 4 | de1.colincogle.name |
| 4 | mail.patrickheyer.com |
| 4 | mail.birdee.at |
| 4 | mail.saschagaspar.net |
| 4 | lab.pikker.ee |
| 4 | turing.lentil.org |
| 4 | promethee.olympe.lurenzu.org |
| 4 | mailu.derewonko.com |
| 4 | ouranos.olympe.lurenzu.org |
| 4 | mail.frykholm.com |
| 4 | mail1.zillner.it |
| 4 | mail.astralus.com |
| 4 | mars.kerschersys.de |
| 4 | useast.colincogle.name |
| 4 | smurb.de |
| 4 | eu.colincogle.name |
| 4 | mail.little-brother.eu |
| 4 | mx1.riseup.net |
| 4 | mail.region46.de |
| 4 | mail.abdene.dk |
| 4 | mx.boxencrypt.com |
| 4 | chaos.olympe.lurenzu.org |
| 4 | dsrun.de |
| 4 | mx.transparent-hosting.eu |
| 4 | mail.server-schwabe.de |
| 4 | mail.delorus.de |
| 3 | celestia.ferretporn.se |
| 3 | mail.fam-schuetzer.de |
| 3 | mail.zeyrox.de |
| 3 | mail.hessis.eu |
| 3 | mail2.alanwest.com |
| 3 | mail6.jth.net |
| 3 | arrakeen.geekwu.org |
| 3 | mail.medien-selber-machen.de |
| 3 | mail-02.own-mail.eu |
| 3 | mail.cpfroehlich.de |
| 3 | promethee.ipv6.olympe.lurenzu.org |
| 3 | mx1.lindenberg.one |
| 3 | ouranos.ipv6.olympe.lurenzu.org |
| 3 | gaia.ipv6.olympe.lurenzu.org |
| 3 | chaos.ipv6.olympe.lurenzu.org |
| 3 | gaia.olympe.lurenzu.org |
| 3 | mail.dermichi.com |
| 3 | ben.mdewendt.de |
| 3 | mail.rootonline.de |
| 3 | mx2.alotof.it |
| 3 | node2.projektzentrisch.de |
| 3 | node1.projektzentrisch.de |
| 3 | mail.kiltran.net |
| 3 | prod-demo000.zivver.net |
| 3 | eclipse.servonline.de |
| 3 | mail.smart-tux.de |
| 3 | mail.smnz.de |
| 3 | mx02.smnz.de |
| 3 | mail.rkfomh.net |
| 3 | mail2.myocastor.de |
| 3 | mail.anguta.net |
| 3 | mail.bluuurgh.com |
| 3 | mx3.alotof.it |
| 3 | mail.dikof.eu |
| 3 | mail.hr2server.de |
| 3 | smtp.picomail.net |
| 3 | hermine.thw-hermeskeil.de |
| 3 | mail2.sheridanwest.com |
| 3 | osmundaregalis.oakforest.in |
| 3 | tim.mdewendt.de |
| 3 | mail.apoorvpal.in |
| 3 | mail.cotsworth.com |
| 3 | mail.goik.de |
| 3 | mail.murgi.de |
| 3 | mail.fuenfer.net |
| 3 | mxbackup.dikof.eu |
| 3 | smtp.bezdeka.de |
| 3 | mail.itc-lucke.com |
| 3 | mali.rattenkot.io |
| 3 | munchen.trost.se |
| 3 | vmail1.greenie.net |
| 3 | mail.ferretporn.se |
| 2 | mail1.theyosh.nl |
| 2 | smtp.ortegamartinez.me |
| 2 | mail.themavlive.com |
| 2 | mx.jgosmann.de |
| 2 | mx.jitsi-meet.de |
| 2 | thylacine3.cfaerber.name |
| 2 | lima.ahrain.net |
| 2 | mail.ahrain.net |
| 2 | venus.br-hq.net |
| 2 | mail.lpcom.de |
| 2 | mail.ls-srv.de |
| 2 | ns4.jth.net |
| 2 | node1.muam.de |
| 2 | node2.muam.de |
| 2 | node1.mucn.de |
| 2 | node2.mucn.de |
| 2 | arsenic.violacea.com |
| 2 | mail.reisingerfamily.net |
| 2 | mail.sajat.net |
| 2 | mail.nsb-software.de |
| 2 | polaris.svanheule.net |
| 2 | mailin02.astralus.com |
| 2 | smtp.virteck.net |
| 2 | mail.xs4me.net |
| 2 | redstonesucht.de |
| 2 | mx.rzrd.de |
| 2 | rz2.siegnetz.de |
| 2 | mail.state-of-mind.de |
| 2 | mail.laponders.com |
| 2 | xenon.blue-neutrino.com |
| 2 | mail.petg.cz |
| 2 | mail.2bis10.de |
| 2 | mx.techthisout.de |
| 2 | mail.boiledscript.com |
| 2 | mail.jordanmlu.nl |
| 2 | mail2.jordanmlu.nl |
| 2 | smtp.misumasu.com |
| 2 | www.bedios.de |
| 2 | hal.ws-team.de |
| 2 | mail.pleijster.nl |
| 2 | mail.xn--tmpfel-3ya.de |
| 2 | mail2.xn--tmpfel-3ya.de |
| 2 | mail.zoopnet.de |
| 2 | mail-prod.standaardplatform.nl |
| 2 | mx.fibianet.dk |
| 2 | mail.ednodarvo.io |
| 2 | mail2.theyosh.nl |
| 2 | mail.z7.dk |
| 2 | mx2.cert.ee |
| 2 | mx3.cert.ee |
| 2 | mail.cghc.de |
| 2 | merlino.alchemistowl.org |
| 2 | mail.blafasel.at |
| 2 | zimbra.dreamradio.org |
| 2 | mail.giblet.eu |
| 2 | smtp.dasuku.de |
| 2 | mail.post-x.org |
| 2 | delorus.de |
| 2 | mail.patthemav.com |
| 2 | ocean.trasno.org |
| 2 | sada.trasno.org |
| 2 | mail.tuxlinux.eu |
| 2 | mail.primaudialrecords.com |
| 2 | andromeda.divjak.at |
| 2 | mail.pasion.ro |
| 2 | lnsph.fr |
| 2 | mail.finsas.de |
| 2 | vps.o2r.fr |
| 2 | mail.fortmail.de |
| 2 | stargate.divjak.at |
| 2 | smx001.mao.systems |
| 2 | smx002.mao.systems |
| 2 | exitus-xzx.secur.com |
| 2 | mail.genano.de |
| 2 | mail.grenz-bonn.de |
| 2 | srv.hermessrv.de |
| 2 | mailstore.ab-data.us |
| 1 | mjtverhoef.nl |
| 1 | mail.n0n.nl |
| 1 | mail.narrowcastingbysmash.nl |
| 1 | mail.netwerk-profs.nl |
| 1 | nhasselt.nl |
| 1 | poortvlietdelft.nl |
| 1 | mail.prelution.nl |
| 1 | mail.router-profs.nl |
| 1 | mail.rowanbalm.nl |
| 1 | ruudadviseert.nl |
| 1 | mail.smash-cb.nl |
| 1 | mail.smashcb.nl |
| 1 | mail.theyosh.nl |
| 1 | mail3.theyosh.nl |
| 1 | mail.u00.nl |
| 1 | mail.ubiquiti-profs.nl |
| 1 | mail.unifi-profs.nl |
| 1 | mail.wifi-profs.nl |
| 1 | mail.woohooyeah.nl |
| 1 | mail.xonlineserver.nl |
| 1 | mail.xs2net.nl |
| 1 | ulrika.berget.nu |
| 1 | mail.fimpen.nu |
| 1 | mail.mingxu.one |
| 1 | mx.sportvereine.online |
| 1 | adblockextreme.org |
| 1 | mail.alolise.org |
| 1 | mail.asprion.org |
| 1 | mx2-nyc.calyxinstitute.org |
| 1 | mail.email-online.org |
| 1 | mail.akerman.eu.org |
| 1 | melusine.eu.org |
| 1 | cumin.exim.org |
| 1 | mx3.freesources.org |
| 1 | mail.gentoo.org |
| 1 | mail.gkbs.org |
| 1 | com.krot.org |
| 1 | mail.mdevries.org |
| 1 | mail.negroniclub.org |
| 1 | mail.papy-team.org |
| 1 | mail.plevenlab.org |
| 1 | backupmx.smartsailing.org |
| 1 | mail.smartsailing.org |
| 1 | coruna.trasno.org |
| 1 | mail.ts-it24.org |
| 1 | mail.vanmastrigt.org |
| 1 | mail.wissenschafftfreiheit.org |
| 1 | mail.wissenschaftfreiheit.org |
| 1 | mail.muesli.party |
| 1 | mx.orzechot.pl |
| 1 | mx.teslamed.pl |
| 1 | puzio.waw.pl |
| 1 | mx1.zerotrust.plus |
| 1 | mail.cored.pro |
| 1 | mail.loftrek.ro |
| 1 | mail.my-cloud.rocks |
| 1 | mail.sbspp.ru |
| 1 | mx.sbspp.ru |
| 1 | mail2.coffes.se |
| 1 | flisanetwork.se |
| 1 | nikesec.se |
| 1 | mail.tobiaseriksson.se |
| 1 | mx2.serv.site |
| 1 | email.sorriaux.software |
| 1 | mail.kuhmunity.space |
| 1 | mx1.kuhmunity.space |
| 1 | mx.r2w.tech |
| 1 | mail1.jan.tm |
| 1 | mail.azerov.tv |
| 1 | mail.klardenken.tv |
| 1 | mail.juniperchick.co.uk |
| 1 | mail.martiniclub.co.uk |
| 1 | mail.sanctus.co.uk |
| 1 | mail.juniperchick.uk |
| 1 | sarahlicity.me.uk |
| 1 | mail.incognito.org.uk |
| 1 | test.theaccessibleweb.uk |
| 1 | mail.civitas.vc |
| 1 | mail.da.wtf |
| 1 | mail.411000.xyz |
| 1 | mail.737900.xyz |
| 1 | smtp.hllr.xyz |
| 1 | mail.dorian.amsterdam |
| 1 | mail.pomazan.xyz |
| 1 | catdoesboom.art |
| 1 | mx01.skyforge.at |
| 1 | birdsonghouse.be |
| 1 | emailus.be |
| 1 | mail.rkrrecycling.be |
| 1 | glasgestaltung.biz |
| 1 | mail.inbox4.biz |
| 1 | mail.informaticadigital.com.br |
| 1 | mail.uranux.com.br |
| 1 | mail.ler.cordeiro.nom.br |
| 1 | omail.ler.cordeiro.nom.br |
| 1 | mail.alternativehosting.ca |
| 1 | mail.alternativeinternet.ca |
| 1 | mail.brinton.ca |
| 1 | mail.dragonhawk.ca |
| 1 | mail.gregoryyoung.ca |
| 1 | mail.wildcove.ca |
| 1 | mail.joergi.ch |
| 1 | mail21.ch |
| 1 | mail.mailgott.ch |
| 1 | mx.demi.cloud |
| 1 | mx2.demi.cloud |
| 1 | mx.siebel.cloud |
| 1 | mx1.cyberpro.club |
| 1 | mail.sunsun.co |
| 1 | mail.20dragons.com |
| 1 | adblockextreme.com |
| 1 | mx64.adelton.com |
| 1 | mx66.adelton.com |
| 1 | mail.agent-est.com |
| 1 | mx02.aixzellent.com |
| 1 | mail.alternativehosting.com |
| 1 | mail.annemarielaponder.com |
| 1 | mx1.azumail.com |
| 1 | mx2.azumail.com |
| 1 | melisandre.darkspacelab.com |
| 1 | mx2.dermichi.com |
| 1 | digilicious.com |
| 1 | mail.disgruntledcode.com |
| 1 | mail2.disgruntledcode.com |
| 1 | mail.dm4productions.com |
| 1 | mail.estroh.com |
| 1 | mail.experiencetherave.com |
| 1 | mail.facubo.com |
| 1 | flisanetwork.com |
| 1 | genehightower.com |
| 1 | mail.goowiz.com |
| 1 | mail.hohenloher-molkerei.com |
| 1 | mail.hostingalternative.com |
| 1 | mail.istar-link.com |
| 1 | pmg.itc-lucke.com |
| 1 | mail.juniperchick.com |
| 1 | mail.kincke.com |
| 1 | mail.kostalli.com |
| 1 | mail.liverado.com |
| 1 | mail.martiniclubuk.com |
| 1 | smtp.mastarin.com |
| 1 | orange.meinprovider.com |
| 1 | mail.mojootti.com |
| 1 | mx-01.nakene.com |
| 1 | mail.negroniclubuk.com |
| 1 | neverwasinparis.com |
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