Business email is a web-based email system. Your email messages, address book, and other account information are stored on our servers, rather than on your computer (POP mail users, however, may download email messages to their own email clients). Because of this, simply viewing your email using the webmail interface does not make your computer vulnerable to regular computer viruses.
Attachments or links sent along with email are not a threat to your system if you do not download or click on them. However, if you choose to download an attachment by either opening it or saving it to your computer, your computer does then become vulnerable to computer viruses. The same is true of all files you download to your computer, whether they are email attachments or not. Clicking unknown links can install malware on your computer.
Business email automatically scans all incoming and outgoing attachments for viruses using Norton AntiVirus, and alerts you to any known viruses it detects in attachments.
It is generally recommended that you do not download attachments or other files, or click emailed links from a source that you do not know and trust and that you install up-to-date anti-virus software on your computer, and download the latest virus definitions frequently.
Following these suggestions should reduce your likelihood of experiencing trouble from computer viruses.
For additional security information, visit the Yahoo Security Center.