[QUOTE=emsr2d2;836413]I have these three sentences, too, please.
1) I always receive a lot of letters & and mail but today I received only a few letters and mail.
[COLOR=Red]This can all be one sentence and I have removed all the commas. They're not necessary. My only question is what you think the difference is between "letters" and "mail". They're effectively the same thing. Did you mean "letters and emails"

-a million thanks for being helped by you,emsr and Jed.
To answer your your question:these examples are among my exam of grammar, so as my book indicated that mail is noncount nouns where as letters are count noun. This mean we can't say mails, is this right?