Frequently Asked Questions and Answers

Click on a question to show the answer.

General questions

How do I install or update MailCheck?

During the initial installation, the installation program asks if a "normal" or "portable" installation should be performed. In most cases, the normal installation is the better way, since the normal installation contains a function for creating a portable version, which takes over all settings from the normal installation.

If a normal installation already exists, the installer will update it without asking many questions. All settings are retained. For an update, you do not need to uninstall before.

Even a portable installation can be updated with the installation program. Since MailCheck does not save any settings in Windows for the portable version, the user must manually select the installation directory. However, you should not mix the normal and portable version, otherwise there are problems with the settings.

Where does MailCheck save its settings and how can I save it, eg to transfer it to another computer?

The settings can be easily saved via the menu item "Export settings ..." from the file menu of the MailCheck window. This creates a registry file that can be imported just as easily. Use the menu item "Import settings ...". Experts can also find the settings in the registry under the key HKEY_CURRENT_USER\Software\Dirk Jansen\MailCheck.

The portable version stores the settings in the mailcheck.ini file located in the program directory. This file also controls whether MailCheck is started as a normal or portable version, so if this INI file is present, MailCheck starts as a portable version.

How does the spam filter work and what do I have to enter there?

MailCheck's spam filter uses what are known as DNS-based filter lists, which do not filter using e-mail addresses which can be easily forged, but use lists of e-mail servers that are known to send spam. Two recommended lists are those accessible via the domains and and both return as a result.

Details on the configuration of the spam filter can be found here:

Why does my virus scanner report a virus or a trojan?

Prior to the release of a new version, MailCheck's installation archive will be reviewed on the site with more than 50 virus scanners, so it is very likely a false alarm. You can even upload the affected file to virustotal and have it checked with the latest signatures. If only your virus scanner sounds the alarm, you should send the file to your antivirus vendor for further analysis with a request to update their virus signatures. For example, Avira offers an appropriate form here.

Why is MailCheck still displaying my messages even though I have retrieved them with my email program?

MailCheck always shows the current contents of the Inbox. MailCheck only changes messages if you delete them with MailCheck. If you now retrieve the messages with your e-mail program, they will remain on the server - in particular in the inbox of the server. Nevertheless, to see the messages no longer in MailCheck, there are the following possibilities:

  • Move the messages in your e-mail program from the Inbox to another folder. This can be another folder on the server (works only with IMAP) or a local folder on your hard disk. MailCheck will no longer display these messages after the next query.
  • In MailCheck, select the option Hide e-mails already marked as seen under "Edit server" in the "IMAP4 Options" tab. Then the Inbox is retrieved with a filter, ie e-mails marked as read are not retrieved by MailCheck and thus no longer displayed. There are some broken servers that mark messages as read on the server after MailCheck's query. You notice this wrongdoing of the servers when MailCheck displays the Inbox as completely empty after the second poll. Unfortunately, you will have to deactivate this option again.
  • Alternatively, you can use the Hide e-mails oder than x days option, which can also be found under "Edit Server" in the "IMAP4 Options" tab.
  • When using POP3 you can deactivate the option "keep mails on server" in your e-mail program.
How can I configure Outlook or another e-mail program in MailCheck?

The program path of the e-mail program can be found as follows:

  1. Search in the start menu Outlook or the desired e-mail program.
  2. Right-click to open the context menu.
  3. Click on "More" -> "Open file location".
  4. Right-click the link for the e-mail program to open the context menu again.
  5. Click on the "Properties" of the link.
  6. In the properties dialog, the required information can be found on the "Link" tab in the input field "Target".
  7. Use the clipboard to copy the contents up to and including ".EXE" into the "E-mail program" field of MailCheck.
  8. The command line usually remains empty.
How can I enter the Mail App or the App as an e-mail program under Windows 10?

Starting Windows 10 Apps from the command line is a bit more complicated, but can be done via the Explorer. To do this, enter the following:

App Settings
Microsoft Mail App E-Mail Program: C:\Windows\explorer.exe
Command line: shell:appsFolder\microsoft.windowscommunicationsapps_8wekyb3d8bbwe!microsoft.windowslive.mail Mail App E-Mail Program: C:\Windows\explorer.exe
Command line: shell:appsFolder\4659BB81.WEB.DEMail_9r8rjdwa12808!App
Why are no notifications shown in Windows 10 when new emails arrive?

In Windows 10 it is possible to supress notifications. Please check the settings in Windows 10 found under "System" and "Notifications and Actions". On this page you must enable app notifications. Furthermore in the list at the bottom the entry for MailCheck must be enabled, too. For testing the notifications use the MailCheck's "Basic configuration" page "Notification" and press the "Test" button besides "Show balloon tips".

Problems with the query

MailCheck can not retrieve my messages and I always get a red exclamation mark. What can I do?

MailCheck displays an error message in the MailCheck window in the server list under Status in case of error. This error message often also contains the exact answer of the server and gives hints to the fix. A detailed error log can be called up via the context menu of the entry. Click the right mouse button on the entry and then on 'Show error details...'.

The following table shows examples of error messages and their possible causes:

Error Possible Cause
Cannot login!

Authentication failed

The login details were not accepted, i. H. Username or password are incorrect and need to be corrected. Some providers require special passwords for retrieval, which must be generated by the provider exclusively for retrieval via POP3 or IMAP. Please see the question Why can't I retrieve my messages? for more information.

Connection Timed Out

If the incoming mail server is set correctly, this could indicate a problem with the firewall or the virus scanner. Please see the question Why isn't the message retrieval working even though I set up everything correctly? for more information.

SSL Certificate Verfication Failed: Self Signed

certificate verify failed

This means that the security of the data connection could not be successfully checked. This is often caused by virus scanners that "eavesdrop" on the data connection. Please see the question Why isn't the message retrieval working even though I set up everything correctly? for more information.

Why can't I retrieve my messages?

Some providers allow the retrieval by foreign e-mail programs only after explicit activation.

Provider Explanation

For AOL you need to create an app password. Details can be found here and here.


With GMX, the querying must be explicitly enabled for POP3 and IMAP. Details can be found here.


Google enforces an advanced login process on email accounts that MailCheck does not support.

Alternatively, you may generate an app password. This generates a separate password for MailCheck. Instructions can be found here.

The advance login process is called OAuth 2.0 and an implementation in MailCheck requires an audit by Google, which would cost a five-digit amount. For this reason, MailCheck will not be able to support OAuth 2.0 for Google accounts.


Microsoft 365 accounts may require app passwords for third party applications.

Details can be found here:

T-Online / Telekom

T-Online allows the retrieval by foreign e-mail programs only after explicit activation.

Details can be found here, for example:


A special e-mail password must be set up for access to Vodafone. The so-called Internet password does not work.

Details can be found here.


Yahoo enforces like Google an advanced login proecess on email accounts that MailCheck does not support. Alternatively you can use so called app passwords which are used for a single application only. More information can be found here.

Why isn't the message retrieval working even though I set up everything correctly?

Some virus scanners block the retrieval of encrypted messages because they can not scan them. To fix this problem, the e-mail virus scanner must be set up correctly. For this purpose, for example, the virus scanner's e-mail checking must be switched off or an explicit activation must be set up.

The following information has kindly been made available by other users and may no longer be current. In this case, the manufacturer should be able to help.

Manufacturer Explanation

Hints about Avast can be found here:


Details about Avira can be found here:


Information about GData can be found here:


Infos about Kaspersky can be found here:


There are no known problems with the Microsoft firewall or virus scanner.

For some antivirus programs, you have to disable the certificate check in MailCheck for getting the retrieval to work because the programs break the SSL connection. This is strictly a man-in-the-middle attack and undermines the security of the connection. To turn off SSL certificate validation in MailCheck go to "Edit Server", switch to the tab "Protocol Settings" and activate the option "Always accept SSL Certificate". This step is necessary because virus scanners only inject their self-issued certificates into more common used e-mail programs - MailCheck is unfortunately not among these programs.