LYNN – They often come in envelopes post stamped from places like South Africa, Nigeria or Canada. But what’s inside shouldn’t be taken as a friendly greeting.Fake checks notorious for defrauding vulnerable people out of thousands of dollars are mailed to residents across Massachusetts every day. And police are once again reminding citizens to beware.”It goes without saying that people should be leery about any type of letter that involves a lottery,” says Lynn police spokesperson Lt. David Brown. “If it’s too good to be true, it’s probably a scam.”Brown is speaking about a fraudulent check that was mailed to a 65-year-old Lynn man on Monday for $4,500. A letter with the check stated he’d just won a lottery, and to receive the $4,500 he would first have to wire $3,000 in “fees” to a woman in Toronto, Canada.The letter was postmarked from South Africa.Luckily for the victim, he reported the mailing to police before sending any money.The same could not be said for a 24-year-old Saugus woman who lost $4,900 in a similar scam earlier this week.According to police, she received a letter saying she had won $480,000 in a sweepstakes. With the letter was a fake check for $4,900. The woman was advised to cash the check and then wire the money to pay a “non-government service tax” before she could receive the $480,000.After she wired the money, the check was returned from the bank as a counterfeit.”That’s a red flag, having to send money in order to receive it,” Brown said. “To send money to Canada or Africa, that’s also a red flag.”Brown adds that oftentimes the language on the checks is awkward or the spelling of words is incorrect.