diff --git a/BusinessLogic/BusinessLogic/UserLogic.cs b/BusinessLogic/BusinessLogic/UserLogic.cs
index c2f21ba..63e8130 100644
--- a/BusinessLogic/BusinessLogic/UserLogic.cs
+++ b/BusinessLogic/BusinessLogic/UserLogic.cs
@@ -11,8 +11,12 @@ using Contracts.ViewModels;
 using Microsoft.Extensions.Logging;
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using System.Net.Mail;
+using System.Reflection;
 using System.Text;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 
 namespace BusinessLogic.BusinessLogic
@@ -30,11 +34,15 @@ namespace BusinessLogic.BusinessLogic
 
 		public UserViewModel Create(UserBindingModel model)
 		{
-			ArgumentNullException.ThrowIfNull(model);
-			// Проверяем пароль
-			_validatePassword(model.Password);
+			// Проверяем модель
+			_validate(model);
+			var usr = _userStorage.GetElement(new() { Email = model.Email });
+			if (usr is not null)
+			{
+				throw new AccountException("An account with that email already exists.");
+			}
 			// Хешируем пароль
-			model.PasswordHash = PasswordHasher.Hash(model.Password);
+			model.PasswordHash = PasswordHasher.Hash(model.Password!);
 			var user = _userStorage.Insert(model);
 			if (user is null)
 			{
@@ -92,13 +100,9 @@ namespace BusinessLogic.BusinessLogic
 
 		public UserViewModel Update(UserBindingModel model)
 		{
-			ArgumentNullException.ThrowIfNull(model);
+			_validate(model);
 
-			if (model.Password is not null)
-			{
-				_validatePassword(model.Password);
-				model.PasswordHash = PasswordHasher.Hash(model.Password);
-			}
+			model.PasswordHash = PasswordHasher.Hash(model.Password!);
 			var user = _userStorage.Update(model);
 			if (user is null)
 			{
@@ -112,10 +116,7 @@ namespace BusinessLogic.BusinessLogic
 
 		public string Login(string email, string password)
 		{
-			if (email is null)
-			{
-				throw new AccountException("Email is null");
-			}
+			_isValidEmail(email);
 			var user = _userStorage.GetElement(new() { Email = email });
 
 			if (user is null)
@@ -123,7 +124,7 @@ namespace BusinessLogic.BusinessLogic
 				throw new ElementNotFoundException();
 			}
 			// Проверяем пароль
-			_validatePassword(password);
+			_isValidPassword(password);
 			if (!PasswordHasher.Verify(password, user.PasswordHash))
 			{
 				throw new AccountException("The passwords don't match.");
@@ -131,12 +132,36 @@ namespace BusinessLogic.BusinessLogic
 			return JwtProvider.Generate(user);
 		}
 
-		public void _validatePassword(string? password)
+		private void _validate(UserBindingModel model)
+		{
+			ArgumentNullException.ThrowIfNull(model);
+			_isValidPassword(model.Password);
+			_isValidEmail(model.Email);
+		}
+
+		private void _isValidPassword(string? password)
 		{
 			if (string.IsNullOrWhiteSpace(password))
 			{
 				throw new AccountException("The password is null.");
 			}
+			var hasMin8Max15Chars = new Regex(@".{8,15}");
+			if (!hasMin8Max15Chars.IsMatch(password))
+			{
+				throw new AccountException("The password must not be less than 8 or more than 15 characters long.");
+			}
+		}
+
+		private void _isValidEmail(string? email)
+		{
+			if (string.IsNullOrWhiteSpace(email))
+			{
+				throw new AccountException("The email is null.");
+			}
+			if (!MailAddress.TryCreate(email, out _))
+			{
+				throw new AccountException("The email is not valid.");
+			}
 		}
 	}
 }
\ No newline at end of file