Hi,

I have three domain names in one Linode (only 1 IP address). All three of them send and recieve emails perfectly (postfix + dovecot + mysql). The problem is that i get marked as Spam in too many email providers (hotmail, gmail, ...). After a while of doing follow ups of my emails i found that im marked as Spam because i just have one reverse DNS; this leaves the other domains i host in a bad place. Is there a way to fix this issue?

Thanks for any help

What makes you think the reverse DNS is the problem? It is a normal and expected case that the domain of the reverse DNS will not match the domain of the email being sent. All that is likely to be checked by email receivers is that you have a reverse DNS entry for the IP and maybe that that name resolves back to the same IP.

Do you have SPF & DKIM set up?

Thanks for the reply.

Ive tried several online email checking websites and thats the only thing they complain about. SpammAssassin doesnt complain, SPF is fine, Sender ID is fine and im not in any email black list. They just complain about reverse DNS and not having DKIM (ive read its not a cause of problem, even though im not really sure. In a few hours ill try to set it up).

Allso just read something about DNS PTR, wich i cant yet get to understand cause its a new concept for me, but seems to be be able to affect email "health".

Hope to hear any good ideas for fixing this issue

Thanks !!

When you connect to a remote machine it will look at your IP address (eg 1.2.3.4) and do a PTR lookup (equivalent of "nslookup -type=ptr 4.3.2.1.in-addr.arpa"). That will get a name "machine.example.com". It will then do a lookup of that name ("nslookup machine.example.com") and expect to see "1.2.3.4" as one of the results.

If this fails then you have a rDNS lookup issue.

(The same thing also happens for IPv6 if you make an IPv6 connection).

This name need not match the email domain name. It's perfectly fine to send mail with "fred@example.com" from a server not in the example.com domain; e.g. from a google server.

_________________
Rgds
Stephen
(Linux user since kernel version 0.11)

Thanks again for the efford in helping me

Reverse DNS set up correctly but still having the same issue. Ill try to get DKIM working (i guess in dovecot) and hopefully it will work ... if not im out of ideas.

Thanks !

PS- maybe its me, but it seems that getting email to work 100% is like trying to make a dinosour move.

In addition to what's been said about PTR/A lookups (if these don't match, mail will often go straight to /dev/null), there's this bit about HELO/EHLO names:

RFC 5321, section 4.1.4:

"An SMTP server MAY verify that the domain name argument in the EHLO command actually corresponds to the IP address of the client. However, if the verification fails, the server MUST NOT refuse to accept a message on that basis."

While this "MUST NOT" end up in /dev/null (assuming the receiving server is RFC compliant), it certainly may be tagged as spam based on this check alone.
Personally I find that insane but I've seen it happen.

To the OP:
Check that the HELO/EHLO reported by your mail server matches the forward (A) and reverse (PTR) records of its IP address, like so:

server.domain.tld > IP address (A record)
IP address > server.domain.tld (PTR record)
HELO/EHLO: server.domain.tld (placebo to please google's, hotmail's and other's asinine anti-spam configs)

For Postfix, the EHLO is set with the myhostname directive:

myhostname = server.domain.tld

SPF/DKIM... yeah I use them, but they don't really have a lot of impact on whether your mail will be classified as spam or not.
IF you use them, make sure you got them right, or else they'll really hurt you. Badly. With a vengeance.

Other than that, well don't get blacklisted (which very rarely happens by accident) and don't hang around in bad neighborhoods (Linode's IP blocks have excellent reputation, for which I congratulate them).

That "MUST NOT" may allow the message to be sent to /dev/null. What it means is that the SMTP server can't reject the connection based on the HELO/EHLO value.

_________________
Rgds

Stephen

(Linux user since kernel version 0.11)

DKIM didnt do the trick either

Ill try to dig into the info draoidh gave (thanks) ... Host name, DNS, Etc. By far i think this is the most complex daemon to set up in Linux. Pisses me off because it really works like a charm, sendeng and recieving emails really quick. Basically its just hotmail and gmail that send the emails to the Spam folder, tried with other email servers and they are cool with my emails. Maybe hotmail/google have a public email policy that i can get hold of to make things work.

THANKS.

https://support.google.com/mail/answer/81126

... interesting over all info from google gmail ....

Did you view the raw message in Gmail / Hotmail to see what the headers say? Sometimes there's a clue there.

_________________
sleddog

Sorry for leving the post un attended ....

Things are working now. The three keys here are SPF, DKIM and DNS. SPF is easy to set up, DKIM is "weird" but following howtos found in google you can get it to work and DNS is easy to set from Linode. In my case DNS records was the key to make my setup work.

1- Make reverse dns to mail.domain1.com
2.- Create 2 entries as mx in domain1.com: mail.domain1.com and mail.domain2.com
3.- in each domain add this txt values:

name / value
v=spf1 a mx ~all
default._domainkey / v=DKIM1; k=rsa;p=((your key here))
_adsp._domainkey / dkim=unknown

Hope this helps