Resolving "Connections to the server on the default ports timed out" in Mac Mail
The error message “Connections to the server somehostname.com on the default ports timed out” in Mac Mail indicates that your email client is unable to properly establish a connection with the email server. This is most commonly caused by incorrect mail server settings configured in the mail client.
Check server settings in Mac Mail
If you are using SiteGround as your email provider you can find the correct server settings to use in Mac Mail in your Site Tools > Email > Accounts, choose the problematic email account and go to kebab menu > Mail Configuration and select Manual Settings tab. Note down all the configuration items on that page.
Then, open to your Mac Mail client and go to Mail -> Preferences. Click the Accounts tab, select your email from the accounts list and click the Server Settings tab.
Compare the server settings here with the settings from Site Tools and ensure that all of them match, especially the ports. Once you are done changing the existing settings to the ones from Site Tools, click Save in order to apply the changes. Allow up to a minute for the new settings to take effect and test the functionality of your email account again.