How secure is sending passwords through email to a user, since email isn't secured by HTTPS.
What is the best way to secure it? Should i use encryption?
You should never send passwords in the clear, nor should you store them in the clear. You should hash them using a slow one-way cryptographic hash such as bcrypt or PBKDF2. If a user forgets their password, you offer them a "reset password" function, which sends a one-time reset link to their account.
A scheme such as the following is reasonable:
I highly suggest reading through The Definitive Guide to Forms-Based Website Authentication for a full set of guidelines on how to build secure login systems.
Email is not secure. Sending a password over email is thus a security risk. To mitigate the risk, you can (in some situations) make it so that the password sent by email is a one-time password, which only unlocks the possibility for the user to select a new password of his own.
This is what good I-forgot-my-password-for-this-Web-site systems do: the user clicks on the button "dammit, I forgot my password", and an email is sent, which contains a URL (with HTTPS) which embeds a random session identifier, and points to a page which lets the user choose a new password. The URL is the "one-time password". With this scheme, you can at least, from the server side, know when the URL was used.
If you can do encryption properly, i.e. if you can send an OpenPGP or S/MIME message encrypted with the user's public key, then the user has a private/public key pair: in that case, why would you use passwords at all ?
It is bad practice to send passwords to the user, as that would mean that you have a cleartext copy of the users password.
I can think of no good reason to do this. There are other more secure ways of accomplishing what is needed.
For a general answer with regards to email security, I suggest you read this link, which has some good information in it.
If you HAVE to send sensitive information over email, use a scheme like PGP or other encryption techniques to secure the data.
If you have the 'clear password' to send in the first place (aside from the registration process), you're doing it wrong. Never, ever store the plaintext password! Lots of companies like Sony Music and the like have been being burned lately from that.. and let me tell you the consumers are not happy.
Echoing the previous posts, email is certainly not safe and you should never email any sensitive data, in particular passwords. Especially since they are not encrypted and our found in clear text, it is extremely easy for anyone to hack into your email and gain access to these across the public network.
If you or your client have trouble remembering your passwords, you should use a secure password manager. This is a website that houses a list of your passwords in a completely encrypted vault. Good ones are KeePass or LastPass.
If you are a company that is trying to send clients their password again, you should have security questions set up that the customers answer when they initially create their account. This way if they forget it, they can click on a link that sends them to answer these questions correctly and reset their password.
For your own knowledge, this is an informative blog, which makes the case for encryption and warns against using certain passwords http://www.ziptr.com/blog-last-4-digits-ssn-password from Ziptr.