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  • mail @example.com without dns a-record for example.com

    From Salvador Mirzo@21:1/5 to All on Sun Dec 22 13:05:41 2024
    XPost: comp.mail.sendmail

    Followup-To: comp.mail.misc

    The objective here is just learning how things work. I asked
    myself---is it possible to get mail sent to someone@example.com without
    an a-record fore example.com? I think the answer should be ``yes''
    because I thought an SMTP would do a type-mx dns query, learn that
    example.com mail is handled by mx.example.com, would get the ip address
    of mx.example.com and reach the server just fine.

    So I made an experiment using my domain---example.com, say. I've been
    geting mail just fine every day. Then I deleted the a-record for
    example.com. My mail system is not really dependent on it in any way as
    far as I know. So the experiment has the set up:

    # host -t a example.com
    example.com has no A record

    # host -t mx example.com
    example.com mail is handled by 10 mx.example.com.

    # host -t a mx.example.com
    mx.example.com has address 1.2.3.4

    But after the deletion of the a-record example.com, I noticed Gmail
    seems not to deliver emails to me anymore. As soon as I created it back
    and send a new message, it arrived just fine.

    Is is just Gmail or is there more I don't understand?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Grant Taylor@21:1/5 to Salvador Mirzo on Sun Dec 22 10:36:00 2024
    On 12/22/24 10:05, Salvador Mirzo wrote:
    Is is just Gmail or is there more I don't understand?

    Per RFCs, email is supposed to prefer the MX record and the host name
    therein.

    Gmail does things by their own rules.

    My only question is, does the MX record also get removed when you remove
    the A record? I've seen questionable DNS administrative interfaces
    remove the entire record, not just the specific resource record.



    --
    Grant. . . .

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Claus =?iso-8859-1?Q?A=DFmann?= @21:1/5 to Salvador Mirzo on Sun Dec 22 12:22:19 2024
    Salvador Mirzo wrote:

    The objective here is just learning how things work. I asked

    You might want to read the fine RFCs, e.g., RFC 5321
    5.1. Locating the Target Host
    ....
    The lookup first attempts to locate an MX record associated with the
    name. [[...]]

    myself---is it possible to get mail sent to someone@example.com without
    an a-record fore example.com? I think the answer should be ``yes''

    Correct.

    But after the deletion of the a-record example.com, I noticed Gmail

    Since you haven't given real data it's hard to say what you did
    wrong. Maybe your MX record is incorrect or hasn't propagated yet.

    --
    Note: please read the netiquette before posting. I will almost never
    reply to top-postings which include a full copy of the previous
    article(s) at the end because it's annoying, shows that the poster
    is too lazy to trim his article, and it's wasting the time of all readers.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Kalevi Kolttonen@21:1/5 to In comp.mail.sendmail Salvador Mirz on Sun Dec 22 18:07:57 2024
    In comp.mail.sendmail Salvador Mirzo <smirzo@example.com> wrote:
    [...] after the deletion of the a-record example.com, I noticed Gmail
    seems not to deliver emails to me anymore. As soon as I created it back
    and send a new message, it arrived just fine.

    Is is just Gmail or is there more I don't understand?

    The email standards do not require a-record so this must
    one of Gmail's quirks.

    br,
    KK

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Levine@21:1/5 to All on Sun Dec 22 21:00:05 2024
    If you want help, you need to tell us the actual domain. Otherwise we'd
    just be guessing what you did.

    According to Salvador Mirzo <smirzo@example.com>:
    Followup-To: comp.mail.misc

    The objective here is just learning how things work. I asked
    myself---is it possible to get mail sent to someone@example.com without
    an a-record fore example.com? I think the answer should be ``yes''
    because I thought an SMTP would do a type-mx dns query, learn that >example.com mail is handled by mx.example.com, would get the ip address
    of mx.example.com and reach the server just fine.

    So I made an experiment using my domain---example.com, say. I've been
    geting mail just fine every day. Then I deleted the a-record for >example.com. My mail system is not really dependent on it in any way as
    far as I know. So the experiment has the set up:

    # host -t a example.com
    example.com has no A record

    # host -t mx example.com
    example.com mail is handled by 10 mx.example.com.

    # host -t a mx.example.com
    mx.example.com has address 1.2.3.4

    But after the deletion of the a-record example.com, I noticed Gmail
    seems not to deliver emails to me anymore. As soon as I created it back
    and send a new message, it arrived just fine.

    Is is just Gmail or is there more I don't understand?


    --
    Regards,
    John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
    Please consider the environment before reading this e-mail. https://jl.ly

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Grant Taylor@21:1/5 to Kalevi Kolttonen on Sun Dec 22 22:07:16 2024
    On 12/22/24 12:07, Kalevi Kolttonen wrote:
    The email standards do not require a-record ...

    Not for the domain name with the MX record.

    But there needs to be an A and / or AAAA record for the FQDN that the MX
    record references.

    ... so this must one of Gmail's quirks.

    I wonder if this might be a Google'ism wherein they saw / cached an A
    record and are now cross that there isn't one. <something> <something> security <something> false test result.



    --
    Grant. . . .

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Salvador Mirzo@21:1/5 to John Levine on Mon Dec 23 10:08:50 2024
    John Levine <johnl@taugh.com> writes:

    If you want help, you need to tell us the actual domain. Otherwise we'd
    just be guessing what you did.

    Thank you---I appreciate that! The domain is antartida.xyz. So I
    deleted the a-record again. Now we have:

    %host -t a antartida.xyz
    antartida.xyz has no A record

    %host -t mx antartida.xyz
    antartida.xyz mail is handled by 10 mx.antartida.xyz.

    %host -t a mx.antartida.xyz
    mx.antartida.xyz has address 195.88.57.140

    %host -t ptr 195.88.57.140
    140.57.88.195.in-addr.arpa domain name pointer mx.antartida.xyz.

    What do I see now? I see I was confused before because I *am* getting
    e-mails from Gmail. What stopped working for me is my IMAP client that
    for some reason is not seeing the messages arrive after I deleted the
    a-record of antartida.xyz, but then I tried another client and it sees
    them all, so it's a client (Gnus) configuration issue. (That's another investigation I need to make, but it's not important.) I apologize for
    the confusion.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Salvador Mirzo@21:1/5 to All on Mon Dec 23 10:18:58 2024
    Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org>
    writes:

    Salvador Mirzo wrote:

    The objective here is just learning how things work. I asked

    You might want to read the fine RFCs, e.g., RFC 5321
    5.1. Locating the Target Host
    ....
    The lookup first attempts to locate an MX record associated with the
    name. [[...]]

    Thank you so much for the reference.

    myself---is it possible to get mail sent to someone@example.com without
    an a-record fore example.com? I think the answer should be ``yes''

    Correct.

    But after the deletion of the a-record example.com, I noticed Gmail

    Since you haven't given real data it's hard to say what you did
    wrong. Maybe your MX record is incorrect or hasn't propagated yet.

    I was likely confused---I updated you all in a follow-up to John Levine.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Salvador Mirzo@21:1/5 to Grant Taylor on Mon Dec 23 10:23:06 2024
    Grant Taylor <gtaylor@tnetconsulting.net> writes:

    On 12/22/24 12:07, Kalevi Kolttonen wrote:
    The email standards do not require a-record ...

    Not for the domain name with the MX record.

    But there needs to be an A and / or AAAA record for the FQDN that the
    MX record references.

    Here's a passage from RFC 5321 that confirms this:

    --8<-------------------------------------------------------->8---
    5.1. Locating the Target Host

    Once an SMTP client lexically identifies a domain to which mail will
    be delivered for processing (as described in Sections 2.3.5 and 3.6),
    a DNS lookup MUST be performed to resolve the domain name (RFC 1035
    [2]). The names are expected to be fully-qualified domain names
    (FQDNs) [...]

    [...]

    When a domain name associated with an MX RR is looked up and the
    associated data field obtained, the data field of that response MUST
    contain a domain name. That domain name, when queried, MUST return
    at least one address record (e.g., A or AAAA RR) that gives the IP
    address of the SMTP server to which the message should be directed.
    --8<-------------------------------------------------------->8---

    ... so this must one of Gmail's quirks.

    I wonder if this might be a Google'ism wherein they saw / cached an A
    record and are now cross that there isn't one. <something>
    <something> security <something> false test result.

    Thanks for bringing that up. It turns out it just confusion on my part.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Salvador Mirzo@21:1/5 to Salvador Mirzo on Mon Dec 23 22:01:33 2024
    Salvador Mirzo <smirzo@example.com> writes:

    [...] What stopped working for me is my IMAP client that
    for some reason is not seeing the messages arrive after I deleted the a-record of antartida.xyz, but then I tried another client and it sees
    them all, so it's a client (Gnus) configuration issue. (That's
    another investigation I need to make, but it's not important.) I
    apologize for the confusion.

    I had two fetchmailrc (for no good reason) and I updated the wrong one.
    After finding the right one and updating the hostname to
    mx.antartida.xyz, I also had to get a new certificate to match the new hostname. Then my fetchmail was able to pull mail once again and
    deliver it to my IMAP server to tell Gnus (my reader) that I indeed have
    new mail. (Yes, I plan to simplify this as soon as possible. I need to
    learn more about everything.)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)