Yes, this feature is inherent in virtually every webmail service and standalone email client. Due to the prevalence of email spam, all you need to do is mark an email as spam and future emails from that address/domain will be blocked.
However, if you know a specific or domain which is flaming you with offensive emails, then most webmail services will have a "block address" list. While the name of this feature will differ from email account provider to provider, it will be located somewhere in the GUI: all you need to do is enter the email address/domain you want blocked and hey presto.
One issue - if you are receiving alot of spam - is that there is usually a limit to the amount of addresses you can block on a free email account. The number will differ between providers, but you can only usually block 500-1000 address per free email account. For paid "advanced" accounts, you may be able to block an unlimited amount of addresses/domains.
The one problem with blocking an email address of someone who is harassing you: is that they can simple make a new email account and continue to send emails to your account. In such a circumstance you may want to make a new email account and keep it's address circulated amongst trusted friends and family.