W10 hosting has link to webmail https://mail.w10.host/
but I get invalid credentials error when I am trying to login.

My site is active on the hosting (listed as a precondition).

Thank you

write a letter to support, the mail is issued by the administrator when the site is already there and ready, mail is not automatically given to empty accounts. You need to ask separately by mail

Thank you, I already got response from admin and my email account is enabled.

Another question: what are IMAP and SMTP servers (if any) for W10.host email?

IMAP: w10.host 143 by default
POP3: w10.host 110 by default
SMTP: w10.host 2525