How to Fix the “Exchange Server Stops Receiving External Mail” Issue?

Exchange Server users, sometimes, face an issue when the external emails stop coming in. This can hamper the communication flow and impact the business. Therefore, the issue needs to be resolved in a timely manner. In this article, we’ll be discussing the steps to resolve this issue.

Steps to Fix “Exchange server stops receiving external mail” Issue

1. Let’s start from the beginning. Check if there were any changes to the infrastructure which have caused this issue. Tracing back will help you to identify the cause.

2. Next, test the server from outside as there could be issues from the network, blocking the incoming emails on port 25. The other thing is to check that the server is responding to port 25 from the outside. For this, you can use the telnet command as given below.

telnet <mx record> 25

Here, you can check if the server is responsive on port 25. You will get a response from the server with the banner.

At this stage, you have reached the service which is listening to port 25. There is nothing on the network which is blocking the connectivity.

3. The next thing to check is the server’s storage. If the server has no or limited storage, incoming emails will be stopped. If the server ends up with no storage, then you might end up with corrupt Exchange databases or transaction log files, which would unmount the databases.

4. The other thing to check is the queue on the server’s transport role. If the server is being bombarded with spam emails, you could end up with a mail server where the pace of incoming emails is much more than it can handle. For this, you need to open the Exchange Toolbox.

Then, click on the Queue Viewer.

Here, you can see all the incoming and outgoing emails in real-time.

5. The next thing is to ensure that the anti-malware is not affecting your incoming emails. To test this, you can disable the anti-malware using the following command in the Exchange Management Shell. It requires a restart of the Transport Service for the changes to take effect.

& $env:ExchangeInstallPath\Scripts\Disable-Antimalwarescanning.ps1

To confirm that the anti-malware has been disabled, run the following command.

Get-TransportAgent “Malware Agent”

After this, make sure to test the incoming emails. Enable the anti-malware if this is not the case.

With this, it will be assumed that all the services of Exchange Server, which were set as automatically start, are all started.

6. You need to also check if all Exchange databases are mounted (see the screenshot below).

If the mailboxes which are not receiving emails are on the database which is not mounted, emails will not be received. There could be many reasons why a database would not mount. However, the common reason is that the logs or databases are damaged due to hardware issue, software issue, or human error.

It would be a big problem for the business if no emails are coming in the system. Also, the business will lose these emails if there is no queue server from a third-party company. This could be a disaster for the business. It is important to always check and monitor the servers and services. However, even if you constantly check the server and services, disaster would strike. In such a case, you can rely on a third-party application to recover from the disaster and services are restored as soon as possible.

Applications, like Stellar Repair for Exchange, can really make a difference when you’re facing issues with your Exchange Server, mailbox database is not mounting due to missing log files, or corruption in the mailbox databases. With Stellar Repair for Exchange, you can open corrupted EDB files from any version of Exchange Server. This Exchange EDB Recovery Tool makes browsing through the multiple EDB files easy with a very clean interface and exports to PST and other formats. You can also export recovered database directly to a live Exchange database or Office 365 tenant. This will make recovery from a disaster much easier. By using the application, you can avoid hopping to another version when migrating corrupt database from Exchange Server 2010 to Exchange Server 2019.

The application has some other useful features, like prioritizing recovery of VIP users, user matching, parallel recovery for performance and efficiency, and the ability to continue recovery if interrupted. There is no limit on the sizes of mailboxes or the EDB files that it can open.