There are reports going around of a Critical Patch Update spoof email being sent that include download links and claims to be from MDaemon Support using the email sender address
As a reminder, always check the “From” address sending domain to ensure it is mdaemon.com. While I’m not one to tell you what to do and I’m very likely not your boss, emails from unusual addresses are spoofed messages and should be ignored and you absolutely should not follow the links or install whatever this spoof is providing.
Are you using Let’s Encrypt with MDaemon or SecurityGateway (or anywhere else)? If so, great! But due to a bug re-validating CAA records, Let’s Encrypt will be revoking a subset of otherwise valid certificates. This bug has existed since 2019-07 and therefore could apply to any certificate issued prior to the fix which was applied 2020-02-29.
So what should you do? Well, luckily there is a tool to check your certificate, so you should check to see if your certificate is being revoked and if so, issue a new certificate as quickly as possible.
Modern browsers don’t check certificate revocations immediately or on all requests, so just because your browser works does not mean there is no impact! If your certificate is revoked you may see an impact some time in the next week or so, or you might not see it at all while users of other operation system / browser / client combinations may have a different experience.
If you happen to be using an external mail filtering service or appliance, one of the critical setup steps is to ensure that MDaemon is configured to not accept messages that attempt to bypass your mail filtering service as spammers look ways to bypass filtering gateways.
There are multiple ways to accomplish this in MDaemon, but one of the easiest ones is often overlooked: IP Shield. IP Shield is a very simple feature, it provides an administrator a simple way to tell MDaemon to only accept mail from a particular domain if it matches one of the listed IP addresses. Once upon a time, this was used to prevent spammers and others from forging one’s own domain, but there are better ways to accomplish this in MDaemon now, so today, we’ll use IP Shielding in another way: By using wildcards. With a wildcarded sender domain, you can use IP Shield to ensure that MDaemon will only accept mail if it’s from a pre-defined IP address or uses authentication.
Open the Security menu
Click on Security Settings
Under Sender Authentication, open the IP Shield dialog
Uncheck Do not apply IP Shield to messages sent to valid local users
Check Do not apply IP Shield to authenticated sessions
Check Do not apply IP Shield to Trusted IPs
Check IP Shield honours aliases
Uncheck Check FROM header against IP Shield
In the Domain field, enter *
In the IP field, the IP address of your mail filtering gateway
Repeat these steps to add any other IPs that should be allowed to send mail without authentication.
Note that you can use wildcards and CIDR notation for IP addresses here.
Since users should be configured to use authentication, this will not impact normal user traffic, but it will block any unauthenticated attempt to send mail unless the IP matches one of the entries.