I tried to set up my homepage on Amazon with Amplify. I added my domain and then it created a hosted zone in Route 53. At my domain provider (ionos) I replaced the name servers with the Amazon servers. Now my homepage is working hosted by Amazon. But the Amazon name servers also influenced my email at ionos. It’s not working any more.
Is it possible to have the homepage at Amazon but the email at my domain provider?
I have a similar setup. As Mark B mentions in the comments, you need to configure your MX records in Route53 correctly. If someone is sending mails to an address that belongs to your domain, the Mail servers will check the MX records to figure out where to deliver emails to.
For IONOS, these values are region-specific. German customers typically have to set the MX records to mx00.ionos.de and mx01.ionos.de Docs in German, while customers of IONOS.com use the .com TLD Docs.
That's for receiving messages, if you're also using your domain to send messages, you should set up DKIM, SPF and for your convenience autodiscover records. IONOS has documentation for these features, otherwise your messages may end up in spam folders.