Spam filters judge the whole email, including who sent it and how its links are wrapped, so adding links can be enough to tip an email into spam. Most fixes are on the sending side. If your emails with AddCal links land in spam or show a warning, try these:
Authenticate your sending domain with SPF and DKIM, and DMARC if you can. Your email platform's help center explains how.
Avoid link shorteners around your AddCal links.
Try sending with click tracking turned off in your email tool, so the links are not rewritten.
On the Business plan, use a custom domain so your event links read from your own domain. See Use a custom domain.
These are general deliverability steps. Each email provider filters differently, so they improve your chances but cannot guarantee inbox placement.
Still flagged?
Contact us with a screenshot of the warning and the email platform you send from, so we can investigate.