Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.
Q: I debated with my peers that we can use the word emails when referring to more than one and it would be grammatically right. But most of them said since we don't say we received mails today, similarly we won't say we received emails . Quick advice please.
A: 
Dan Bron's comment (above) that e-mail/email at its inception was treated as a mass noun is correctand so is Kristina Lopez's comment (above) that e-mail/email is widely applied today not just to the medium of electronic mail but to individual messages sent and received in that medium. For many years the technology magazines where I worked enforced a strict house rule: e-mail (and later email) referred to 'electronic mail' as a mode of communication, and individual messages had to be termed 'e-mail [or email] messages.' But three or four years ago, the overwhelming weight of popular usage prevailed, and we began to accept the use of email as a singular noun that could take an indefinite article, and emails as a plural nounboth referring to individual messages. It is probably not coincidental that other forms of electronic communication receive similar treatment in popular (and some publishing) usage: a text and texts for 'a text message' and 'text messages,' respectively; and an IM and IMs for 'an instant messaging message' and 'instant messaging messages' (as I recall, people used to avoid 'instant messaging message' by conflating the technology with the individual message to produce 'instant message'). At publishing houses, the proper handling of 'an e-mail [or email]' versus 'an e-mail [or email] message' remains a house style issuethere is no universally agreed-upon preference. If you are beholden to no one's style guide, you are free to use the wording that you like better. But the overall tendency, I believe, is toward accepting an email and emails as collapsed forms of 'an electronic mail message' and 'electronic mail messages.'