After I upgraded to 4.7, when I click on a link in an E-Mail notification I get from chrome 

Quote

This page is not working
www.*****.de has forwarded you too many times.
Clear your cookies.
ERR_TOO_MANY_REDIRECTS

Where can I start to look at? Thank you.
 

It appears your site has at least one update or patch pending. Please visit your ACP -> Support page and check for a box with an orange alert about an update, then process it.

Does the same problem happen?

If it does, please then disable all 3rd-party items (apps, plugins, and themes), then trigger an email notification.

Does the same behavior then happen?

1 hour ago, Mark H said:

It appears your site has at least one update or patch pending. Please visit your ACP -> Support page and check for a box with an orange alert about an update, then process it.

There was only one optional patch available. I applied it. Links in emails are not working.
Then I disable all customizations, sent an test email, links in this e-mail are not working. Sorry.

Thank you, I've opened a ticket for this issue.

Someone will contact you via that ticket when they are able.