Apple Mail SSL Certificate Trust Warning

Mail server changes may result in an Apple Mail SSL certificate trust warning.

Some email client programs, such as Thunderbird, gmail and kmail, give the ability to permanently accept the warning and continue as normal.

However, Apple Mail does not permit this certificate trust warning to be ignored, or addressed as a valid exception.

Similarly Microsoft Outlook may permit a temporary security exception, but may not permit a permanent exception.

It is possible to workaround this warning IF you trust the new SSL certificate. The error message will give details that can be used to help you decide if you trust the certificate or not. The workaround is to reference the mail server by its hosting configured name, rather than the domain name.

I used a terminal program to get the IP address of the mail server


and then took the IP address to look up its name


An entry such as was given.

This entry could then be used in place of the website domain in the configuration of the incoming and outgoing mail servers.

Apple Mac email add Local Subfolders

I like to store email locally, divided between personal and work email.

Copying emails locally allows me to set my email to delete the older emails from the server. Keeping me below the restriction on the mailbox

For work emails I use sub folders to divide up my administration and the different projects.

Using Thunderbird, this is easy to implement: simply create additional sub-folders below the Local Folders.

The aim is to replicate this using the Apple Mac email program

Apple Mac Email add Subfolders: Side Menu

In the image below can be seen a part of the side menu for an Apple Mac email program.

Added to this is the smart menu for the domain VNTweb.

Apple Mac Email add Subfolders: add new Folder

Additional sub folders can be added below the smart mailbox.

To add a new folder, or Mailbox as Apple calls it, hover over the mailbox to show the circled plus icon. Click on this icon to show a dialogue allowing the location to be selected and a name given for this new mailbox.

For the new top level mailbox/sub folder I left the location alone and
entered the name “Projects“.

I then added two new sub folders/mailboxes below this. You may wish to select Projects as your location, of maybe like me drag the Customer 1 mailbox below Projects by dragging it into the Projects folder.

Now to test the use of this mailbox.

In your Inbox pick one of your existing emails. Drag it into the Customer 1 mailbox. Keep the command button down to copy rather than move.

I checked that the email was still available from another computer and email program.

I then deleted the email from the inbox. Unfortunately both emails were now gone.

I was able to drag an email into the new sub-folder mailbox. It would then disappear from the inbox. If I copied the email to the mailbox, deleting it from either mailbox also deleted it from the other.

I considered the use of a Mailbox as opposed to a smart mailbox

For this I clicked on the Mailbox menu entry, across the top menu. From the dropdown menu I selected New Mailbox.

Apple Mac Email add Subfolders: New mailbox

From the familiar New Mailbox dialogue I chose On My Mac as the location. Adding a Mailbox name of Projects.

Under the Smart Mailboxes I now had a new section.

Apple Mac Email add Subfolders: Smart Mailboxes - On My Macon-my-mac

I was able to crate new sub mailboxes as I had done previously.

Of particular interest I found that emails copied into these sub folders/mailboxes were more permanent. They didn’t disappear if I deleted them from the inbox

By adding a simple Mailbox to the On My Mac location, with appropriate sub Mailboxes I was able to copy emails into this directory structure. This allowed me to save and group emails related to projects, incorporating both sent and received emails. Emails copied in this way were immune to the deletion of the original in the inbox.

Don’t forget to send yourself some test emails so that you can confirm that this is working for you. Software development has a habit of making changes which alter our previous experiences.

Warning: Remote Host Identification has Changed

Using terminal program on Apple Mac book pro I had following error when connecting to a Linux server

Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
Please contact your system administrator.
Add correct host key in /Users/neil/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /Users/neil/.ssh/known_hosts:6
ECDSA host key for has changed and you have requested strict checking.
Host key verification failed.

The server had been recently rebuilt with revised ssh server configuration.

I opened another terminal session and edited the file .ssh/known_hosts using vi. ecdsa-sha2-nistp256 MIGeMA0GCSqGSIb3DQEBAQUAA4GMADCBiAKBgGacCUIonaql4oszZ1QFBxDxVD898cZH+UaPglM71NSad9b5MBHcTIOVEHNjSj7BBW3YMxI45fvg/He8zA94IJw1LR84zz1JwfmtEmD4VWt9pw8KRKmFKRI7X+rvsCknRJcpOHC7GQqYD4IHU6kzIqBNAfMn6YGzRo7XXhxgmwkbAgMBAAE= ecdsa-sha2-nistp256 MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCVoNuBxLq4QKwcYhXh06PU7LQHCKSdQEbEVUzEIZS46dCjrIosp73+ulbqfUGPG4GlduKG98CzdijoFS2t+C9Kq3A48uMxdPRfhhOCutWl+fLmLY2G7WgM+/8nAB07SQhtgNeNH55TCvOlsrkaEGdsek1ZePNsJbiRRL+UCG7sJQIDAQAB ecdsa-sha2-nistp256 MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCFzyPNE4K/g55XU2fV3vNZNv/A6EE26zB1VLmiZPGFJpqJdLsvwSFiQx0T4LOJMoCXxiCjiyexd5hQyh0s3euWBWdn25TmsNToMmRosrkbfJGnKYj12ZUTuuOIgVwfxlAroHmf7m0gl+Yx43s7eeXVRn2cnwCHziZN2E5X+RqoowIDAQAB ecdsa-sha2-nistp256 MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCHaOo07u4NFIBQxMenPfKSjV06+77TEgaWhiyvoIpQvP0udBVbvJuOD3EpBXLNDV9Z4jeCofrqy4mJRqP08Wq/r6EFny8i34EQm/VJNzLqvNhJ76JzVaYJYmL/CSKGklHjYGktUCq4rHTcxoUlcL9uvfXO2raWsnOFgBIZJt/KzwIDAQAB

Deleting the previous entry for the server and ssh to the server once more.

The authenticity of host ' (' can't be established.
ECDSA key fingerprint is SHA256:8wZ3n0MN2c1YzOdYZ01Ct+MVDm924tmfw4NUfAnMenA.
Are you sure you want to continue connecting (yes/no)?

I selected yes and was able to access

Interesting – my computer (Debian) has these entries encrypted.

Change Mac Computer Name

The Mac computer name is configured from the Sharing Settings.

Hover the mouse over the apple at the top left of the screen and click on System Preferences in the drop down menu.

Mac System Preferences

Click on the Sharing icon, at the end of the third row.

Mac System Preferences Sharing

In the texbox labelled as Computer name enter the new name for the computer.

Close System Preferences to complete.

Take a Screenshot on a Mac Computer

How to take a screenshot on a Mac and capture a window or part of the screen.

Looking for command shortcuts to take screenshots on a Mac computer for use in posts on this website I found these to use.

Capture Complete Screen

The key combination used to take a screen shot on an Apple Mac computer is:

Command (⌘) + <SHIFT> + 3

By default the screenshot is automatically saved to the desktop.

This is similar to using Print Screen on a Windows or Linux computer.

Capture a Window

To capture a single window

Press Command (⌘) + <SHIFT> + 4

The mouse cursor changes to a crosshairs with numeric location. Its actual location isn’t relevant at present.

To select the window for the screenshot capture click on the Space bar to change the cursor to a camera. The window under the camera will be dulled, like the background of a lightbox. Move the cursor over the window to be selected and click on the mouse to complete the selection.

The screenshot of the window is saved to the desktop.

Capture Part of the Screen

A refinement on selecting a window and then cropping for the desired part is to capture a part of the screen. this may be across parts of windows, or a section of a window.

To begin the selection press Command (⌘) + <SHIFT> + 4

To select the area click on the start point. Keep the mouse key depressed, whilst dragging the selection box to cover the desired area to be captured.

If you wish to move the top left corner of the selection box press the <SPACE BAR> whilst moving the mouse.

Take care, releasing the mouse key will cancel the selection process, saving a copy of the selected area.

Changing the Saved directory

By default the captured images are saved to the desktop.

Changing where Mac saves screenshots is actioned via the terminal command.

Changing Where Mac Saves Screenshots

Changing the directory where a Mac saves screenshots is easy but not as expected.

I was anticipating that changing the directory where a Mac saves the screenshots would be configured from within System Preferences.

I found that to set the directory is actioned from a terminal window.

From the App Launcher click on Other and then click on the Terminal application. Within the terminal enter the following and press <RETURN>.

defaults write location ~/Documents/Screenshots

To apply the changes, which you have made, enter the following in the terminal window, and press <RETURN>

killall SystemUIServer

I have found that I prefer to have my screen shots instantly available for use.

From the desktop I can easily drag them into the folder relevant to the project. It also saves opening two folder views.

If you wish to change back to the default desktop then enter

defaults write location ~/Desktop

Once again to action the change SystemUIServer is killed for changes to take effect.

killall SystemUIServer

Enable Mac Firewall

Purchasing a new Mac computer I was surprised to find that by default the Mac firewall is turned off. The Mac firewall settings are readily managed from the System Preferences.

To enable the firewall on a Mac computer begin by opening System Preferences.

To open System Preferences click on the Apple icon at the top left of the screen and select System Preference from the drop down menu.

Mac System Preferences

On the top row of icons click on the icon Security & Privacy.

Mac System Preferences Security and Privacy

From the options at the top of the Security & Privacy window click on the Firewall tab.

Mac System Preferences Security and Privacy Firewall

To be able to make changes to the firewall settings this window needs unlocking. To unlock this settings window click on the padlock in the bottom left corner of the window.

Mac System Preferences Security and Privacy Firewall Unlock

Enter your login details and click on Update, to unlock the firewall settings window.

Mac System Preferences Security and Privacy Firewall Unlocked

With the padlock unlocked, click on the option Turn On Firewall. The firewall on the Mac Computer is now enabled.

Mac System Preferences Security and Privacy-Firewall on

Having enabled the firewall you may wish to visit he advanced options.

Mac System Preferences Security and Privacy Firewall Advanced

Where is the Apple Mac Delete Key

The Apple keyboard has the backspace key in the upper right hand corner of the keyboard, but where is the Delete key?

Often its possible to backspace and delete the preceding characters.

For example with the cursor at the start of a word it is more natural to delete from that point forward as opposed to positioning the cursor at the end of the word and deleting backwards.

Viewing the keyboard of a MacBook Pro there are no additional key characters, as often shown in blue for actions paired with another key.

Viewing the keyboard I considered the pairing of the backspace key with one of these keys is most likely: fn, ctrl, alt, cmd.

To delete forwards on a MacBook keyboard air the <fn> key with the backspace: <fn> + backspace.

How to Hide the Apple Dock Launcher

The Apple Mac dock launcher can occupy valuable screen real estate. Hiding the dock bar of icons is just a simple combination of keys.

The key combination of <cmd> + <Option> + D can be used to hide and show the dock bar at the bottom of the screen.

What is the Mac f5 Refresh Key Equivalent

Familiar with the Windows or Linux f5 key to refresh a bowser – what is the Mac keyboard equivalent f5 refresh key?

Whilst the Apple Mac keyboard includes the f keys at the top of the keyboard the same functions from Windows and Linux are not repeated.

In a browser to refresh the page content the equivalent of holding down the f5 key is command + R.