Blocking an undesirable email address in Apple Mail on your iPhone, iPad, or Mac can help you manage your inbox and avoid spam or unwanted correspondence. Follow these steps to block a sender across your Apple devices using the Mail app.

On iPhone and iPad:

1. Open the Mail App 

Launch the Mail app from your home screen.

2. Find the Sender’s Email 

Navigate to an email from the sender you wish to block.

3. Access Contact Options 

Tap on the sender’s name at the top of the email to open a contact menu.

4. Block this Contact 

In the dropdown menu, choose “Block this Contact”. Confirm if prompted.

5. Manage Blocked Contacts in Settings:

– Go to “Settings” on your device, scroll down, and tap on “Mail”.

– Scroll down to the “Threading” section.

– Tap on “Blocked”.

– Here you will see a list of blocked contacts and you can add or remove contacts as necessary.

On Mac:

1. Open Apple Mail 

Find and click on the Mail icon in your Dock or open it from your Applications folder.

2. Select an Email from the Sender 

Click on an email from the sender in question to select it.

3. Block Sender 

With the email selected, go to the top menu bar, and choose ‘Message’. From there, select ‘Block Sender’.

4. Manage Blocked Senders

– Open Mail and go to “Mail” in the Menu Bar.

– Choose “Preferences”, then click on “Junk Mail”.

– Under the tab, you can oversee blocked senders and edit your list as needed.

Once a sender is blocked, emails from that address will be moved automatically to your Junk folder in Apple Mail on all devices where you are signed in with your Apple ID.

Please note that sometimes updates or specific versions of iOS/macOS might slightly alter these steps. Always ensure that you have the latest version of Apple’s operating system on your device for all features to work correctly.