It can mean they're screaming at you, they have no clue that cap lock and bold are on, or they don't know the netiquette that says it's impolite to use all caps. Or the keyboard could be broken.
Either the person is shouting at you when writing in all caps, or they're trying to emphasize a point
It means they are Shouting.
All email addresses are in small caps, as are all internet addresses. If you are typing internet or email addresses in large caps, you are in fact "doing it wrong".
On the Internet, ALL CAPS is considered SHOUTING! Very few posts need to use all caps. Limit the use of capitalization for when something is really important.
Some people may like it when others write or type in all caps. Other people may be ignored because they are typing or writing in all caps. It is up to the human eye to determine whether they prefer caps or lower case.
Common unspoken rules. For example: ALL CAPS IS CONSIDERED YELLING>
Any word that is all caps in email signifies that the writer is yelling.
Using all caps on the internet should be avoided, including in your e-mails. The reason you should avoid using all capital letters is because of Internet etiquette rules. Using all caps is interpreted as shouting.
It is like shouting on the computer.
Writing your name in all capital letters can suggest emphasis, assertiveness, or a desire to stand out. It can be seen as a bold or commanding way to present your name in written form.
Swear Misspell use all caps abreviate sarcasm
It is rude, the equivalent of shouting. It is difficult to read, and does not allow for correct sentence structure. Something that people fail to realize about email is that your correspondents draw many conclusions about you from how your messages look. If they are not constructed as an educated person would, they will probably assume that you are uneducated. It's like walking around in public picking your nose, but most folks don't get it.
Replying an email is pretty simple. All you have to do is select 'Reply' and then you write what you have to say, add a period (.), and then select 'Send'.