Plesk is set up to use SmarterMail as mail server.
While creating or updating email address. the following error is reported:
Internal error: Can't open domain. Domain: domain.tld [domain.tld]. Reason: You have already attempted to log in too many times within a short period. You must wait a set amount of time before trying again. If you require assistance, please contact your email administrator. (Error code 1)
Integration of Plesk with SmarterMail is broken.
Go to Tools & Settings > Server Components > Mail Server and submit working SmarterMail administrator credentials.
Add SmarterMail site in IIS as suggested in this article .
Register SmarterMail as the default mail server by executing below commands:
C:\\>%plesk_bin%\\defpackagemng.exe --get --force
C:\\>%plesk_bin%\\defpackagemng.exe --update --type=mailserver --package=smartermail