Upgrade of Dr.Web can be performed only by uninstalling the outdated Dr.Web version followed by installing a new version using the installation file with the update.
To upgrade Dr.Web
•Download the latest installation package of the program from the official Dr.Web website 
. For this, enter a valid serial number in the corresponding field.
•Remove Dr.Web. For this:
1.Run the update installation file drweb-[version]-av-exchange-windows-x64.exe with the update. The Installation Wizard will open.
2.The Installation Wizard will detect the installed Dr.Web and prompt you to upgrade to a new version. Click Update.
3.Stop the Microsoft Exchange Transport service. To do this, click Open the list of services link, right-click the service in the list and then click Stop. Once the service is stopped, click Next.
4.If you want to save current application settings for further use, select Save settings. Click Remove.
5.During the application removal process, the transport agents for Microsoft Exchange Server 2007–2019 in SMTP transport system are deleted using Exchange PowerShell, where you need to confirm the removal by entering Yes (or Y). When transport agents are deleted, enter the exit command to close Exchange PowerShell.
6.To complete the application removal, you need to restart the computer. Click Restart now or Later.
The Installation Wizard will open again after the restart.
•Install Dr.Web with the update. For this:
1.Read and accept the terms of the License Agreement by selecting I accept the terms of License Agreement.
Click Next.
2.Stop the Microsoft Exchange Transport service.
To do so, click Open the list of services link, right-click the service in the list and then click Stop. Once the service is stopped, click Next.
3.Select the licensing type. You can register your license later, specify the path to the valid license key file or use the key file from the central protection server if Dr.Web Agent is installed on your computer. Click Next.
4.If the Save settings option was selected during the application removal you will be prompted to use the saved configuration or delete it and re-configure the application after installation. Click Next.
5.Before starting the installation procedure, click Installation parameters to configure the following parameters: Install transport agents and Install VSAPI.
You can also enable the transport agents installation and registration monitoring by selecting the Enable transport agents monitoring option. During the installation on Microsoft Exchange Server, transport agents are registered in SMTP transport system by Exchange PowerShell, which does not close automatically, so you will need to enter the exit command manually to complete installation.
Click OK.
6.If you selected the Enable transport agents monitoring option when configuring thee installation parameters, you need to exit the monitoring window after the transport agents are installed and registered. The "Dr.Web AntiVirus Agent enabled" and "Dr.Web AntiSpam Agent enabled" messages in PowerShell indicate the successful agents registration by Microsoft Exchange Transport service. Enter the exit command in PowerShell.
7.Once the installation is complete, click Exit.