If your subscribers mark your Mailchimp campaigns as spam then your Mailchimp account will be suspended or disabled. If your hard bounce rates are high then Mailchimp will disable list importing and other single opt-in methods.
What does disabling single opt-in mean?
The message as below doesn’t mean that Mailchimp have disabled your account or are stopping you from sending email marketing. Rather, they are, per the warning message, disabling single sign-on sources and forcing double opt-in for all new subscribers. Your existing subscribers in your lists remain as they are however any new subscribers will need to double opt-in. This does mean that importing from Excel and other sources has been disabled.
There is no simple way to get around the double opt-in of subscribers. The best thing to do is exactly what Mailchimp states in that new subscribers need to double opt-in (i.e. your new subscribers will receive a confirmation email which in which is a hyperlink that they’ll need to click to verify that they do want to be subscribed to your list). This is frustrating but it’s likely that Mailchimp will remove the restriction after awhile.
How do I avoid getting single opt-in disabled?
In Mailchimp classes almost every participant that attends training has a requirement to import subscribers in bulk usually from Microsoft Excel. The disabling of single opt-in means that this import can’t be performed.
The simplest means of ensuring that your hard-bounce rates remain low is to initially only import email addresses that you’ve either recently added to your list or that you’ve recently successfully sent an email to.
On an ongoing basis it’s important to send campaigns to your subscribers regularly as this reduced the chances of suddenly having a large number of hard-bounces.
Why does Mailchimp care about hard-bounces?