Hi, To add to what Kyle wrote: didier[~]$ nslookup shellworld.net Server: 2001:861:5872:fed0:56c4:5bff:fe21:679c Address: 2001:861:5872:fed0:56c4:5bff:fe21:679c#53 Non-authoritative answer: Name: shellworld.net Address: 50.116.47.71 didier[~]$ So yes the reverse DNS seems to work for email associated to the domain shellworld.net which has a ptr record. The only thing I note is that the address in the output is an IPv4 one (the same given by "host shellworld.net") but dunno if that matters. Also a query of internet.nl about emails from shellworld.net doen't ring a belle eithre wtr reverse DNS: https://internet.nl/mail/shellworld.net/1280212/ Hence my question for Karen: I have assumed that the domain associated to your email address is shellworld.net, but maybe this issue occurs with another email address, using a different domain? Cheers, Didier Le 6/30/24 à 14:42, 'Kyle' via blinux-list@xxxxxxxxxx a écrit : > john doe' via blinux-list@xxxxxxxxxx alitoa mmaoni: >> What are you talking about, we have no context. > > > If you are unable to help, just say so. I have enough context and > understanding of the subject matter to answer the question. > > > Most receiving mail transport agents reject messages from sending > addresses that don't pass a reverse DNS check,, meaning that they look > back at the DNS IP for the domain portion of the email address to be > sure that the IP points back to a domain. It doesn't need to be the same > domain, but it has to point back to a domain of some kind, which is then > checked against the SPF on the domain portion of the sending address to > be sure that the sending machine is allowed to send from that address. > In the case of shellworld.net, > > host shellworld.net > > shellworld.net has address 50.116.47.71 > > shellworld.net mail is handled by 10 > mx.shellworld.net.cust.b.hostedemail.com/ > > Actually, that mx one is the one we're checking. > > host mx.shellworld.net.cust.b.hostedemail.com > > mx.shellworld.net.cust.b.hostedemail.com has address 64.98.38.4 > > 4.38.98.64.in-addr.arpa domain name pointer mx.b.hostedemail.com > > Actually looks right to me. But just for grins: > > host 50.116.47.71 > > 71.47.116.50.in-addr.arpa domain name pointer users.shellworld.net > > OK I'm out. Sorry, I can't help, as everything here looks right. You > should be able to send mail, and the recipient shouldn't be complaining > about PTR records or reverse DNS. But it could be the SPF on > shellworld.net, which needs to allow mail from > mx.shellworld.net.cust.hostedemail.com. > > dit +short shellworld.net in TXT > > "v=spf1 a:shellworld.net services.shellworld.net mx:shellworld.net > a:atlas.bondproducts.com a:forward.b.hostedemail.com > include:_spf.hostedemail.com ~all" > > Yes, this is also looking right. No problems from my checks, so I really > am out this time. Sorry I couldn't be of any further assistance. > > ~Kyle > > Imetumwa kutoka mikono yangu > > To unsubscribe from this group and stop receiving emails from it, send an email > to blinux-list+unsubscribe@xxxxxxxxxx. > To unsubscribe from this group and stop receiving emails from it, send an email to blinux-list+unsubscribe@xxxxxxxxxx.