I get the message "security certificate can't be verified" accessing my email
When you connect to your email through mail software on your computer or device, you are connecting to your domain through mail.your-domain.com.If you have an SSL certificate for your domain, it will be associated specifically with the generic address (www.your-domain.com) Your mail software brings up a warning when you connect to mail.your-domain.com because that is not the exact domain listed in the certificate.
Your connection will be successful, the SSL certificate will still encrypt your connection, so you can ignore the warning.
If you want to prevent this warning from appearing, your mail client should have the option to accept the certificate permanently despite the warning.
Users who have mail clients on Apple devices are likely to encounter an SSL Certificate Trust Warning when connecting to our mail servers using an aliased name such as mail.your-domain.com. This may be preventing you from connecting to our mail servers to send/receive emails.
To get around this, you should connect to your mail server using its actual hostname, which will be something like mail123.extendcp.co.uk. This can be found by logging into your eXtend control panel.
Alternatively, you can add an exception to the SSL Certificate via Keychain.
If that doesn't work, try changing your mail settings as below...
User Name: Full email account.
Password: The password for this email account.
Incoming Mail Server: insert mail server URL here
IMAP port: 993
POP3 port: 995 (we STRONGLY recommend you use IMAP rather than POP3)
Outgoing Mail Server: insert mail server URL here
SMTP port: 465
You should set the "Secure Sockets Layer (SSL): On" and you should use Password for Authentication method.