There are many different possibilities to answer this question. We will go top down beginning with the browser.
Most of the browsers support the html input tag of type "email" and most of them would automatically warn the user about a wrong format of the address. However there are many standards of email address pattern. Furthermore the user might disable the browser validation, so we should not rely on this.
The second station is the javascript of the browser. Probably the easiest way to validate the email address is to use a regular expression an match the input against this expression. However the user may disable the javascript or send a request in other way than browser. Therefore it's absolutely necessary to validate the email address on the server side. This might be done by a regular expression, but some more sophisticated systems would check the MX record of the domain given in the email address, to be sure it might be a real address of a real mail server.




Encrypting and decrypting emails by S/MIME

1. Configure mail application for example Thunderbird. S/MIME does not work in the browser.
2. Generate your public and private key using for example ssl or extension to your mail application.
3. Create a certificate signing request using for example ssl.
4. Send request to "third Party" authority. There are many free and payed authorities, however the second ones are more trustworthy.
5. Download signed certificate and certificate of the authority.
6. Import signed certificate and certificate of the authority to mail client.
7. Now you can sign your emails by the certificate.

Use "GoAnywhere OpenPGP Studio" to secure email communication

Open PGP is the preferred standard for most banks and financial institutions when transferring sensitive data.
Open PGP is a form of asymmetric encryption where a public key is used to encrypt the file and a corresponding private key is used to decrypt the file. Several encryption algorithms can be utilized within Open PGP, including the Advanced Encryption Standard (AES), to provide a high level of protection. Digital signatures can also be used to sign files to allow the recipient to authenticate the validity of the sender's signature.

"GoAnywhere OpenPGP Studio" can be used as follows for generating public/private key pair, for exporting public keys and for encryption/decryption of sensitive data:

1) Download and install GoAnywhere OpenPGP Studio from

2) Recipient creates new private/public key pair
- Download and install "GoAnywhere OpenPGP Studio".
- choose "OpenPGP Keys" tab
- click "Create" button to generate new key
- enter the required information and click the create button

3) Recipient exports public key
- choose "OpenPGP Keys" tab
- select the key you want to export
- click "Export Public Key(s)"
- choose location where to store the public key

4) Recipient sends the exported key to a person from whom you would like to receive encrypted emails

5) Sender encrypts file
- choose "OpenPGP Tasks" tab
- navigate to the file you want to encrypt and mark it
- click the "Encrypt" button
- choose the key with which you want to encrypt and specify the location where to store the encrypted file
- click the "Ok" button

6) Sender sends the encrypted file per email

7) Recipient decrypts the encrypted file
- choose "OpenPGP Tasks" tab
- navigate to the file you want to decrypt and mark it
- click the "Decrypt & Verify" button
- choose a location where to store the encrypted file

Encrypt email attachment with PGP

Privacy on the Internet is a growing concern, especially as more and more people are using it for their professional and personal business, socializing, and entertainment. Information sent over the internet or by email is not necessarily secure. You don't know how many servers the message will pass through between your computer and the recipient's, or who has access to those servers.


example of a smtp dialog

Connect to an arbitrary mail server on port 25 using telnet
telnet 25

The mail server responds
Connected to
Escape character is '^]'.
220 ESMTP Postfix (Ubuntu)

Type into the smtp session:

The mail server responds:
250-SIZE 40960000
250 DSN

Tell the mail server who is the sender:
250 2.1.0 Ok

Tell the mail server who is the recipient:
250 2.1.5 Ok

Tell the mail server that you want to deliver the actual data:
354 End data with .
Subject: test
Hello World!

Quit your message by using a single dot

250 2.0.0 Ok: queued as 13C248D49E5D

Quit the SMTP session
221 2.0.0 Bye
Connection closed by foreign host.


How to test a mail server?

Which steps have to be done to manually send an email using the SMTP protocol? This can be useful to check after setup if a mailserver is configured properly.


Reject virus messages using Postifx

The Postfix mail server is in place to received and send emails. To improve security incoming and outgoing messages should be scanned for malware. If the scanner detects a virus, Postfix should be reject the message in order to prevent users from receiving malware.

How to send an eMail via PHP?

The core problem of this challenge is to find an existing PHP-function, which enables a programmer to send an eMail. Furthermore, the correct syntax and the required data of the mail-function is an essential problem.

Login at a website without having to registrate

You want to do a login at a website, but you do not want to registrate at the website (for example you do not want to have to wait for an activation of your account, you want to login instantly, you do not want to give your email address to another possible spammer, you only want to login once, etc. )

E-Mail Filters

Many people get huge amounts of mail every day. It can be painful to sort, categorize and handle all those mails manually. Furthermore, it costs a lot of valuable time that you could spend elsewhere. However, there is an automatic approach that can save you a lot of this time: E-Mail Filtering <strong>Challenge:</strong> <ul><li>Choose an E-Mail client (either desktop client or web mail)</li> <li><strong>Create the following filters:</strong></li><li>a filter that automatically labels mails from with "TU" or moves them to a folder called "TU"</li><li>a filter that sends unwanted mails (containing words of your choice) to the spam folder</li><li>a filter that marks e-mails containing the words "Knowledge Management" as important (e.g. by flagging or starring)</li></ul>


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