If you're facing the issues like your emails are landing in a spam folder, then this guide will help you in most cases.
If the DKIM record is corrupted, then it'll cause your emails may landing in a spam folder instead of an Inbox.
Emails go to the Spam folder instead of the Inbox folder when the DKIM spam protection is enabled for the domain in Plesk > Domains > Domain.com > Mail Settings > Use DKIM spam protection system to sign outgoing email messages.
DKIM is marked as Fail in by email services, for example, Gmail or Hotmail.
Follow the steps below:
Log into Plesk
Go to Domains > Domain.com > Mail Settings.
Disable the Use DKIM spam protection system to sign outgoing email messages option.
Press the Apply button.
Enable the Use DKIM spam protection system to sign outgoing email messages option.
Press the OK to button to generate a new DKIM record.
Note: If your domain DNS is hosted externally (Like Cloudflare or Domain Registrar), manually copy the default._domainkey.domain.com record to the external DNS server.
It will fix the issue in most cases, but it needs some time to be propagated.
If you've any questions, please let us know!