First of all, for clarity, emails getting into the clients' spam folders is not a delivery issue as such, but an aspect of how the receiving end (the client's email platform) sorts incoming messages based on automated algorithms. The clients can influence/customize these sorting algorithms, for example by classifying your emails as "not spam", which is basically manual white listing (move the emails into their inbox folder or other email organizing folders they might have when they find the emails in the spam folder).
And people should generally check their spam folders, just in case there is a "false positive" there (which means an email classified by the receiving server automatically as spam out of caution, but is not actually spam). The spam folder acts as potential spam buffer, not as a trash folder where emails are sorted to be deleted and people can forget about them without even checking.
As for why some email servers will automatically classify your Console messages as spam in the first place, there can be several possibilities: wording in emails (repeated expressions, marketing-sounding language), some servers may be more sensitive than others to the fact that the Console sends the emails in the name of your address via a 3rd party email delivery platform (SendGrid), and sometimes people may mark the emails as spam themselves, either knowingly or by mistake.
So, there is no formula of total control from your end over this delivery-into-spam aspect. You can tell clients to make sure they check their spam, white list your messages found in spam (which should increase the possibility of future messages to no longer end up in spam) and the clients could also provide you with a second email address as a back-up, that you can add to their profile email settings, separated from the first address with a semi-colon (;).
One more aspect that will increases significantly your level of control over email delivery is having an email address on a custom domain of your own, where you can add SendGrid as an authorized sender, which implements an official protocol for recognizing incoming emails from authorized sources on the receiving end (leading to less bounced emails and less emails sorted in spam). An FAQ here:
How can I authorize the Coaches Console email server to send in the name of my custom email address?
Should you have more questions about this, please let us know via a support ticket.