The vowel system of English can be confusing because there are only five vowel letters (A-E-I-O-U), but there are 15 different vowel sounds. The key is that each vowel letter has three or four sounds, and it is important to learn the basic sounds of each one.
The letter “E” is a little bit more straightforward that the other vowels, because there is only one Long and one Short sound. So, the basic sounds for the English letter “E” are Long-E and Short-e.
The sound of Long-E is the same as the name of the letter “E” when you say the alphabet. Some common words with this sound are: he / we / be / maybe / she / see / three / seem / feet / seen / feel / street / green / week / deep / free.
Short-e is pronounced in the front middle (not low, not high) part of the mouth — the mouth needs to be open, but not quite as much as for Short-a-1. And of course, it is very important to relax the tongue, if not, the sound of Short-e can be easily confused with Long-A (see Sell or Sale). Here are some frequently used words with Short-e: get / help / tell / end / men / left / next / egg / red / best / ten / less / yet / yes / kept / seven.
Besides the basic sounds, any vowel letter can use the schwa sound. This happens in weak (unstressed) syllables. Here are some words in which the “E” is in the unstressed syllable and has the schwa sound: item / college / faces / escape / define. Also, very frequently used words, which are usually unstressed in sentences, often use the schwa sound; some with [e] are: the / them / then.
The letter “E” is usually silent when it is at the end of a word, as in “safe”. Silent -e can also be found in the middle of a word, when it is in a compound, such as “safeguard” (safe + guard), or when suffixes are added, as in “safely”. (see more about Silent -e).
So, when you see the letter “E” in a word, it will almost always be one of the sounds above. It is very rare to find some other vowel sound used. There are few words with an “E” that do not use one of those sounds, such as: been / new / eye / few / English / they / eight / sew.