Receiving spam is common now a days, no matter how private or secure your email address, it is still defenseless against spam. Ideally, spammers have used many tactics and loopholes to retrieve millions and millions of email addresses.

There are several approaches spammers can take to capture email address, for instance, Email Extractors: These software tools are very skilled at scouring the internet for email addresses. Websites, Forums, Alumni sites, news posts, etc. These robots can locate thousands of email addresses on sites per hour. And spammers run them day and night.

Domain registration records are also a common source used by spammers. Sometimes they send lot of spam using your email address in the "from" field.

So we can't control spammers fully at this time due to lack of standards in anti-spamming.