Messages accepted by hotmail, but never arrives in user's mailbox

We're running our own email server that works great (Office Logic InteChange from LAN-Aces).

But - when sending emails to users at hotmail.com, the email never arrives in their mailbox or in their spam or junk folder.
Sending the same email from a Gmail account works fine.

Have examined our mail server logs, and the message is correctly accepted by hotmail.com. Suspect some kind of internal blocking in the hotmail system, but I'm unable to find a way to check it.
Two questions: Anyone know how to contact the hotmail support for this kind of question (if there is a support....)
Have anyone else experienced this problem with hotmail or have any ideas how to fix it?
Olaf BerliOwnerAsked:
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David FavorLinux/LXD/WordPress/Hosting SavantCommented:
Look very carefully at your SMTP responses from Hotmail.

Normally Hotmail produces SMTP responses which describe any problems.

Might be the problem is showing up later as a bounce.

Check your logs + ensure you've correctly parsed out all the Hotmail SMTP responses + process any non 250s correctly.
Olaf BerliOwnerAuthor Commented:
Thanks for your response.

I've checked the mail server logs carefully, and there is nothing coming back from hotmail the same day or during the following 3 days.

Everything seems normal when sending the message - the dns lookup, the smtp handshake etc.
The last part of our mail server log shows that the message was accepted by hotmail. It looks like this:

18:58:15 04A42C <- 250 2.1.5 Recipient OK
18:58:15 04A42C -> DATA
18:58:15 04A42C <- 354 Start mail input; end with <CRLF>.<CRLF>
18:58:15 04A42C SMTP Sent 2324 bytes in 0.001 seconds (2324000 cps)
18:58:16 04A42C <- 250 2.6.0 <201901021758143767db43d8@interchg.infokomp.no> [InternalId=30288109447087, Hostname=BN3NAM01HT163.eop-nam01.prod.protection.outlook.com] 7984 bytes in 0.402, 19.387 KB/sec Queued mail for delivery -> 250 2.1.5
18:58:16 04A42C -> QUIT
18:58:16 04A42C <- 221 2.0.0 Service closing transmission channel
18:58:16 04A42C SMTP Sending finished
DKnowles2001Commented:
Using the same email server, if you send an email using a different domain name (one without a SPF record) does it get delivered to the @hotmail address?

Cutting a long story short, I had something similar with @btinternet addresses once. At the time BT were migrating their service from Yahoo to another mail provider.

As with your example, the mail server I was working with was reporting the message as being delivered to the @btinternet servers successfully but there was no sign of it in the recipient's mailbox. What I couldn't see was the receiving system's internal message routing. It turned out that the receiving system was routing the messages between servers and changed the sending IP address in the headers, which invalidated my SPF record.

If your situation is similar I see the @infokomp.no domain has an SPF record with -all at the end, instructing the receiving server to drop email from other addresses. Changing it to '~all' might help with delivery, even though your '-all' is perfectly valid.
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David FavorLinux/LXD/WordPress/Hosting SavantCommented:
Ah... I just realized what may be happening.

The user's you're sending to on Hotmail... Drop an update about how you're determining if mail arrives into their account.

Hotmail aggressively uses Recycled Spam Traps which always return 250 during message submission, then immediately deleted the email.

So next bit of information is to clarify what you mean be mail never ends up into an account. Specifically if these are accounts you actively maintain + can do a login + check.

If not. You may be hitting Recycled Spam Traps which... you must scrub from your list immediately...

Hotmail, Oath (Yahoo/AOL), Prodigy all aggressively use Recycled Spam Traps + will add your sending IP(s) to RBL lists if you send to these addresses Recycled Spam Traps repeatedly (meaning you never scrub these addresses).
Olaf BerliOwnerAuthor Commented:
David Favor:  I don't know for sure that the message arrives into the recipient's account. All I know is that it is delivered to a hotmail server and that the recipient can't find it in their inbox or in their spam/junk folder.  I don't have any access to this or other hotmail accounts, so it is difficult to verify. Since I've seen the same thing when sending to other hotmail addresses, I suspect that hotmail is blocking og deleting the messages.

DKnowles2001:  The SPF is something that could make sense....  As you've noticed, infokomp.no (my main domain) has a SPF record pointing to my server's official IP address.
However - I have an email client where I have defined two "personalities" When sending the mentioned messages to hotmail I've been using an address of olaf@berli.no. The berli.no mail server handles only incoming emails to my address (automatically forwarded to my infokomp.no address). Outbound messages are sent through my infokomp.no server. Guess that this could make some problems related to the spf record ??
David FavorLinux/LXD/WordPress/Hosting SavantCommented:
You said, "I don't know for sure that the message arrives into the recipient's account. All I know is that it is delivered to a hotmail server and that the recipient can't find it in their inbox or in their spam/junk folder."

At least you know these are real accounts, if humans are reporting the problem.

Best you open a hotmail account yourself + see if you can replicate the problem.

Note: Your SPF record looks correct + https://dmarcian.com/spf-survey/ also says your record is correct.

Note: Your SPF record for berli.no is broken is missing, so if you send from this recipient your mail will likely never be delivered.

You must fix this 2nd problem first.

Your SPF + DKIM records must be correct for the sender address you're using.

Here's how you find out for sure.

Setup these DMARC records, which are report only (no enforcement)...

# email will be something like dmarc@berli.no or somewhere you receive email...
_dmarc.berli.no.	600	IN	TXT	"v=DMARC1; p=none; sp=none; fo=1; adkim=s; aspf=s; pct=100; rf=afrf; ri=86400; ruf=mailto:dmarc@berli.no; rua=mailto:dmarc@berli.no;"
_dmarc.infokomp.no.	600	IN	TXT	"v=DMARC1; p=none; sp=none; fo=1; adkim=s; aspf=s; pct=100; rf=afrf; ri=86400; ruf=mailto:dmarc@berli.no; rua=mailto:dmarc@berli.no;"

Open in new window


This will cause a DMARC report to be triggered every day + sent to dmarc@berli.no which will tell you exactly what's occurring.

Just refer to the DMARC report generated by Hotmail every day.

You'll likely find that 100% of either SPF or DKIM is failing.

This will tell you exactly what to fix + also, when the reports stop coming in, you'll know all problems are likely fixed.
DKnowles2001Commented:
Hello Olaf,

the SPF record is only applicable to the domain used in the FROM: field. As you are sending from @berli.no and that doesn't have an SPF record then it will not have any affect.

As you don't have an SPF record I ran a quick telnet test using olaf@berli.no from a fixed IP address to a hotmail.com account. The email was delivered successfully to the junk email folder. As such it looks David Favor may be correct and hotmail is secretly dropping email sent from your IP address.

I just checked and you can still create @hotmail.com accounts so if you don't have access to one already you can create a new one for testing.

Create test hotmail.com screenshot.
If you want to test yourself using a different fixed (not dynamic as that would show up on a block list) IP address from a Windows PC you could try the following:

From a command prompt run:

telnet hotmail-com.olc.protection.outlook.com 25

When telnet loads you'll be greeted by the Microsoft ESMTP mail service. Next, enter the following sequence (substitute testaccount@hotmail.com for your own hotmail account):

helo
mail from:olaf.berli.no
rcpt to:testaccount@hotmail.com
data
Subject:Test!



Just a test!

.

quit


Then check your test hotmail inbox and junk folder to confirm the message was delivered. I've assumed you're sending to a hotmail.com address, but the address to telnet to changes if it's a hotmail.co.uk/hotmail.no or other domain. Just lookup the MX record for the one you're sending to.

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Olaf BerliOwnerAuthor Commented:
Hello DKnowles2001 and David Favor.

Thanks for the very good feedback!
I've created a hotmail account and tried several tests. It seems like you are correct, that hotmail classifies emails from my IP-address as spam. It also seems like my address of olaf@berli.no may be blacklisted, because I tried to send from this address through the server where the berli.no domain actually is located. This was also put into the spam folder. The reason for this MAY be that the mail provider for this domain hasn't a SPF record for the berli.no domain. I've told them to set up one, and will see if it changes enything.

Another thing that may have caused my mailserver's IP address to be blacklisted is that the server is also handling mail for a third domain (reverse-therapy.no). This has a SPF record. The server handles a discussion list with approx 25 users. From time to time some of them have a full mailbox, changes their email address etc. which makes it impossible to deliver email to them. I suppose that this could also contribute to a blac-listed IP-address.

I'm very glad for all the good feedback and help I've got from you. Keep up the good work!!

-Olaf-
Olaf BerliOwnerAuthor Commented:
Thanks for very good help at a technical level that was understandable to me.
Keep up your excellent work!
David FavorLinux/LXD/WordPress/Hosting SavantCommented:
Glad you were helped!
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