Gentoo Archives: gentoo-user

From: Kai Krakow <hurikhan77@×××××.com>
To: gentoo-user@l.g.o
Subject: [gentoo-user] Re: Dynamic IP address services.
Date: Sat, 12 Nov 2016 09:45:10
In Reply to: [gentoo-user] Re: Dynamic IP address services. by Ian Zimmerman
1 Am Tue, 8 Nov 2016 11:33:26 -0800
2 schrieb Ian Zimmerman <itz@×××××××.net>:
4 > On 2016-11-08 15:14, Grant Edwards wrote:
5 >
6 > > You need a static IP address _and_ a domain name
7 >
8 > FreeDNS will provide the domain name, assuming you're content with a
9 > 2nd level subdomain. You can examine the Received headers of this
10 > mail to see how that works.
11 >
12 > > with an MX record that points to that static IP address
13 >
14 > MX records are optional. Per the RFCs, a conforming MTA MUST connect
15 > to the address in the A record (provided by FreeDNS, of course) in the
16 > absence of a MX.
18 This is no longer optional as far as I know. MTAs still must do this
19 fallback for compatibility but it is recommended to have an MX record.
21 Some German mail providers even started to deny mails from senders
22 without MX. And lately, one even denied delivering mails to receivers
23 without MX (which somehow violates the above constraint but they
24 convinced me, pointing to an RFC, that this is correct behavior on
25 their site). So I added the missing MX on this particular domain.
27 Getting the MX correct (with matching reverse and forward DNS) is very
28 important to not have your mails classified as possible spam. So I
29 cannot comply with your suggestion that MX is optional. Really: don't
30 do it. Put an MX.
32 BTW: I totally suggest against using a dynamic IP for MX purposes. You
33 never know where your mail is delivered. There's chance that mail is
34 delivered to a stale IP, and there's an SMTP server accepting all your
35 mails. If you really want this, use ETRN at least, which probably won't
36 be supported by the ordinary mail service provider (at least not in
37 etrn-only mode). ETRN is an SMTP command to turn around roles: After
38 authenticating, you can turn around roles and let the remote SMTP
39 server spool all outstanding mails to your local SMTP through a new
40 connection. This means, the destination site on the remote SMTP server
41 has to be configured to put all your mails on the deferred queue until
42 you connect and turn [1]. Still, this means you don't have the MX on
43 your local site, just the second level MX (configured through a
44 transport rule). This is somewhat similar to POP3 grabbing. In this
45 case, the second level MX may be replaced by a simple A record, I
46 believe.
48 [1]:
50 --
51 Regards,
52 Kai
54 Replies to list-only preferred.