I am sending email from my server but now I get this error when I send to certain doman:

The following message to bixx@simnet.is was undeliverable.

The reason for the problem:
The address 185.152.x.x is not allowed to send messages for the address service@xxdot.is

Possible reasons for this problem:
- Wrongly configured SPF records on the sending domain.
- The email is being forwarded to another email address.

Please contact your email provider.
-------------------------------------------------------------
Those are my DNS records

MX            @      xxdot-is.mail.protection.outlook.com      
TXT      -      @      v=spf1 include:spf.protection.outlook.com -all      
CNAME      -      autodiscover      autodiscover.outlook.com

For some reason, a user who has full access to all mailboxes is unable to expand other users boxes in Outlook view. Also his mailbox doesn't always open. When it is not in cached mode an error is displayed:

In cached mode the mailbox opens but usually complains that it is disconnected. Connecting to Exchange fails until it suddenly succeeds.

The problem is very similar as in this topic: https://www.experts-exchange.com/questions/29125111/Intermittently-cannot-open-Outlook-The-set-of-folders-cannot-be-opened-Network-problems-are-preventing-connection-to-Microsoft-Exchange.html 
However in my case the mailbox migration to a different database didn't help.

Our on premises Exchange environment was migrated from Exchange 2010 to 2016 and after that these problems have followed users occasionally. Setting a registry value to prefer IPV4 over IPV6 brought some stability but even after that we've had some reports of these problems. I have a feeling that the problem might be somehow MAPI related and it has to do with the amount of mailbox objects etc.. I know there is a registry value that is mentioned in some discussions that can be raised but others are against messing with Exchanges registry.

Now the full access user and it's mailbox is used for a software that needs to sync data from other users mailboxes. When the sync process tries to run an error is displayed:
Software User: username
PIM Account: username
Error Message: A MAPI related …

Probably a basic one but can figure it out.
I am setting up a Postfix server to accept mail form our LAN and relay it to external WAN.

Mail sent from the LAN devices (MFC etc) get this error:

Remote Server returned '554 5.7.1 Client host rejected: cannot find your hostname, [172.16.255.89]'

172.16.255.89 is indeed the correct LAN IP. How do I authorize it ?

I am Unable to send most emails to most domains. We are using Sophos XG as the sending relay.
All (almost all) emails are stuck in the queue with error:
421 service not available (connection refused, generic failure).
some emails that give these errors sometimes are getting delivered.
Problem started only yesterday!

I sent a message to a friend and it got rejected.  Here's the error I received.
Please help me decipher!

We have a situation where our IPS and sometimes our SPAM filter blocks specific IP addresses that are sending mail from GMail and Google mail. In every instance these blocked IP's are on an Internet black list. Googles' solution is to white list these servers and any other Google servers (literally thousands of them), this is insane to me. I am sure others have encountered this situation and I am wondering how do you handle it.

Dear Experts, is there anyway to search exchange mailbox with exact time range?

For example I 'd like to search an email with ketwork "abc" in content and was received before 2.45pm of 26 Dec 2019?

I tried Search-mailbox command on Exchange 2016 but it did not work

Hi,
How to resolve version below, as I did copy the file from the path below?

C:\Program Files\MySQL\MySQL Server 5.7\lib

We are planning to set up DKIM for a mail domain, example.dk.
I can find a lot of good advice on the Internet. But there's one question I can't find an answer to.
We Use Exchange online for most of our mail, but we also have an on-premise SMTP server for routing mails from our webservers. And we are using a cloud service for our news letter service. How can DKIM be set up when there's multiple systems sending mail from our example.dk domain?
All the guides I have found on the Internet are about a setup with only one mail system.


Best regards Holger Nielsen

Hello Expert

My Customer have migrate to an Exchange server and everything went well.
But when they are trying to check email on the Outlook App on mobile they cant see anything, but the Outlook 2016 is working fine.

Anyone can point me in rigth directions?

Thanks you

A monthly email to me from a company is reported at their end as having been sent, but I don't receive it. It doesn't go into my spam, and the sender along with their IT dept., don't think they are at fault.

Any ideas what I might try to look for or suggest to them as an investigation into this, or a solution?

Thanks,
k.

We have dmarc implemented and I usually collect and review the reports weekly. About 3 weeks ago, the number of threat reports massively jumped and remains alarmingly high. Looking at a 2 month period: October-November, 7k emails passed dmarc, 70k have been reported as threats. This all looks like someone external has tried to use my domain and is failing the spf and dkim checks and I am getting the reports about it. I expect dmarc is working as it should but the volume of emails and the sudden increase around 3 weeks ago is what has got be concerned. Unfortunately I have had no reports from humans in that time of fake email coming from my domain. I do not even know the content of the emails or the recipients. All I know from dmarc is that they exist. My dmarc policy is set to quarantine rather than reject so conceivably people are still seeing the emails. I would appreciate any advice from the email experts here.

I had this question after viewing can I disable Delivery Status Notification for delayed messages and/or undelivery messages?.

How can we do it in Exchange 2016, do we have to restart any service after that?