Unsolicited email is email that an individual did not request. Unsolicited, or junk, email is a widespread problem and this page offers some advice on how to recognise the various sorts of junk mail, what to do about it and how, where possible, to avoid it.
There are several ways that spammers collect email addresses: for instance from institution or personal web pages, mailing list archives, web-based bulletin board messages, Usenet News (including Google Groups) postings, replies to email with 'remove me from your mailing list' links, or simply by guessing likely addresses. You should never reply to spam, because this may confirm that your address works and invite more spam.
If you receive harassing or offensive mail that is directly addressed to you, see harassing mail. The guidelines and the discussion that follows do not relate to harassing and offensive mail.
A common form of unsolicited email is the 'phishing' scam. This is an email that looks as as though it is from a genuine organisation such as a bank, your institutional network or email support, or ISP, and asks you to 'verify' personal details, passwords etc. See 'Phishing - they're after your account details' for further information, including some examples received at Cambridge. The UK Banks also have a site with information about phishing, money mules and trojans - Bank Safe Online.
Chain mail is the email equivalent of paper chain mail. Chain mail may be distinguished from other junk mail if it was sent by a friend or acquaintance and includes a request to forward the mail to as many people as possible.
A particular type of chain mail is the hoax virus warning. This also usually includes a request to forward the mail to everybody you know. See FAQ: How do I know a virus warning is a hoax?
Another common form of unwanted email is just junk mail, usually known as "spam" or UBE (Unsolicited Bulk Email). Typically this comes from an address that you do not recognise, is addressed to an address that you do not recognise and has a subject which suggests that it might be junk mail, for example get rich quick schemes, advertisements for bulk emailing people, advertisements for pornographic sites or direct selling (often pharmaceutical products). The UIS offers a central "spam-scoring" scheme to help you to filter out junk mail. See Dealing with spam and junk email for more advice.
Email worms or viruses can propagate automatically by sending infected email. Virus-generated email often looks more like legitimate email than spam, since it can use information from the infected machine to disguise itself. See Email and the Virus Threat for advice on recognising and protecting against this type of unwanted mail. Virus-generated email often disguises itself so that the message appears to come from an innocent third party; this can cause misdirected security and delivery notifications - see "Collateral Spam" for more information. To protect yourself from viruses, see the UIS's Computer viruses and other malware: what you need to know for guidance. The Central email scanner does provide some protection from email worms and viruses, but you should still run a virus scanner on your own computer.