"Nessus" detected several vulnerabilities on smtp port 25 . Should I be concerned?

We checked several vulnerabilities listed by Nessus in detail as soon as they were brought to our attention. We found that they were in fact false alarms.
SME smtp server is protected from the exact buffer overflow attempts mentioned in the reports from Nessus. Moreover, smtp server runs under a user account without privileges, in a restricted environment which protects the system against compromising attempts.