The shortest valid email address may consist of only two parts: name and domain.

   name@domain

Since both the name and domain may have the length of 1 character, the minimal total length resolves to 3 characters.

well the problem is really the question.. email depends on if it is sent over the internet, or within a closed system (eg intranet). over the internet, I believe x@y.zz is the shortest email possible (e.g. google&#39;s G.CN for china would result in the shortest email adress possible, e.g. i@g.cn, which is 6 characters long). on the intranet however, it is an entirely different thing, and i@y would be possible, which is just 3 characters long.


I believe the standard you are looking for is [RFC 2822 - Internet Message Format][1]

More specific info on email address restrictions in [RFC 3696 - Section 3][2]

To quote the spec:
&gt; Contemporary email addresses consist of a &quot;local part&quot; separated from a &quot;domain part&quot; (a fully-qualified domain name) by an at-sign (&quot;@&quot;).

So three characters is the shortest. 

I originally got this info from [Phil Haack&#39;s blog post][3].


  [1]: https://www.rfc-editor.org/rfc/rfc2822
  [2]: https://www.rfc-editor.org/rfc/rfc3696#section-3
  [3]: http://haacked.com/archive/2007/08/21/i-knew-how-to-validate-an-email-address-until-i.aspx

Many mail-servers will not accept the email-address if there aren&#39;t at least 2 characters before the @.
That doesn&#39;t make it an invalid address, but if the servers don&#39;t know that, it sure can lead to a lot of problems.

I need a query in sql to get total columns in a table.Can anybody help?

To get total number of columns in a table in sql

I am working on some code which uses the pthread and semaphore libraries. The `sem_init` function works fine on my Ubuntu machine, but on OS X the `sem_init` function has absolutely no effect. Is there something wrong with the library or is there a different way of doing it? This is the code I am using to test.

    sem_t sem1;
    sem_t sem2;
    sem_t sem3;
    sem_t sem4;
    sem_t sem5;
    sem_t sem6;

    sem_init(&amp;sem1, 1, 1);
    sem_init(&amp;sem2, 1, 2);
    sem_init(&amp;sem3, 1, 3);
    sem_init(&amp;sem4, 1, 4);
    sem_init(&amp;sem5, 1, 5);
    sem_init(&amp;sem6, 1, 6);

The values appear to be random numbers, and they do not change after the `sem_init` call.

sem_init on OS X

I&#39;m specifically looking for the minimum length of the prefix and domain. 

I&#39;ve seen conflicting information and nothing that looks authoritative. 

For reference, I found this page which claims that a one character email address is functional:

http://www.cjvandyk.com/blog/Lists/Posts/Post.aspx?ID=176

I tried validating email addresses at Gmail and they expect prefix greater than or equal to 6. 

These are obviously way off. 

My web framework expects prefix greater than or equal to 2.

What is the actual minimum length of an email address as defined by the IETF?

I'm specifically looking for the minimum length of the prefix and domain.
I've seen conflicting information and nothing that looks authoritative.
For reference, I found this page which claims that a one character email address is functional:
<a href="http://www.cjvandyk.com/blog/Lists/Posts/Post.aspx?ID=176" target="_blank" rel="noopener noreferrer">http://www.cjvandyk.com/blog/Lists/Posts/Post.aspx?ID=176</a>
I tried validating email addresses at Gmail and they expect prefix greater than or equal to 6.
These are obviously way off.
My web framework expects prefix greater than or equal to 2.

I have a required validation setup on a textbox, but I also have to make sure it is an integer.

How can I do this?

asp.net validation to make sure textbox has integer values

When validating data, I&#39;ve gotten into a habit of doing the following:

**Note:** I don&#39;t really have individual booleans for each check. This is just for the example.

**Another Note:** any error handling during the tests are done properly. The ONLY exceptions thrown in the try-catch are my own.

    try {
      if (validCheckOne = false) {
        throw new Exception(&quot;Check one is bad&quot;);
      }
      if (validCheckTwo = false) {
        throw new Exception(&quot;Failed because of check2&quot;);
      }
      if(validCheckTen = false) {
        throw new Exception(&quot;Yet another failure on your part: check10.&quot;);
      }
    } catch(Exception e) {
      MessageBox.Show(&quot;Your stupid data is wrong! See for yourself: &quot; + e.Message);
    }

Is this bad practice? Does throwing Exceptions slow the program&#39;s execution or is inadvisable?




Is it a good or bad idea throwing Exceptions when validating data?

Which characters make a URL invalid?

Are these valid URLs?

* `example.com/file[/].html`
* `http://example.com/file[/].html`

Which characters make a URL invalid?

is there any way that html element file

    &lt;input name=&quot;file1&quot; type=&quot;file&quot; style=&quot;width:300px&quot;&gt;

only accept PDF files and when we browse its only show PDF files...


Thanks

How to get the HTML&#39;s input element of &quot;file&quot; type to only accept pdf files?

I wanted to know if there is any standard APIs in Java to validate a given URL?
I want to check both if the URL string is right i.e. the given protocol is valid and then to check if a connection can be established.

I tried using HttpURLConnection, providing the URL and connecting to it.  The first part of my requirement seems to be fulfilled but when I try to perform HttpURLConnection.connect(), &#39;java.net.ConnectException: Connection refused&#39; exception is thrown.

Can this be because of proxy settings?  I tried setting the System properties for proxy but no success.

Let me know what I am doing wrong.


Validating URL in Java

I need for testing purposes to populate few hundred email boxes with various messages, and was going to use smtplib for that. But among other things I need to be able to send messages not only TO specific mailboxes, but CC and BCC them as well. It does not look like &lt;a href=&quot;http://docs.python.org/library/smtplib.html&quot;&gt; smtplib &lt;/a&gt; supports CC-ing and BCC-ing while sending emails.

Looking for suggestions how to do CC or BCC sending messages from the python script.

(And — no, I&#39;m not creating a script to spam anyone outside of my testing environment.)

python: how to send mail with TO, CC and BCC?

    &lt;?php
    class Email extends Controller {

        function Email()
        {
            parent::Controller();	
            $this-&gt;load-&gt;library(&#39;email&#39;);
        }
	
        function index()
        {
            $config[&#39;protocol&#39;]    = &#39;smtp&#39;;
            $config[&#39;smtp_host&#39;]    = &#39;ssl://smtp.gmail.com&#39;;
            $config[&#39;smtp_port&#39;]    = &#39;465&#39;;
            $config[&#39;smtp_timeout&#39;] = &#39;7&#39;;
            $config[&#39;smtp_user&#39;]    = &#39;mygmail@gmail.com&#39;;
            $config[&#39;smtp_pass&#39;]    = &#39;*******&#39;;
            $config[&#39;charset&#39;]    = &#39;utf-8&#39;;
            $config[&#39;newline&#39;]    = &quot;\r\n&quot;;
            $config[&#39;mailtype&#39;] = &#39;text&#39;; // or html
            $config[&#39;validation&#39;] = TRUE; // bool whether to validate email or not		

            $this-&gt;email-&gt;initialize($config);

            $this-&gt;email-&gt;from(&#39;mygmail@gmail.com&#39;, &#39;myname&#39;);
            $this-&gt;email-&gt;to(&#39;target@gmail.com&#39;); 

            $this-&gt;email-&gt;subject(&#39;Email Test&#39;);
            $this-&gt;email-&gt;message(&#39;Testing the email class.&#39;);	

            $this-&gt;email-&gt;send();

            echo $this-&gt;email-&gt;print_debugger();

            $this-&gt;load-&gt;view(&#39;email_view&#39;);
        }
    }

I am getting this error:

    A PHP Error was encountered
    Severity: Warning
    Message: fsockopen() [function.fsockopen]: unable to connect to ssl://smtp.gmail.com:465 (Connection timed out)
    Filename: libraries/Email.php
    Line Number: 1641

Using `PORT 25/587`

I got this error:

    A PHP Error was encountered
    Severity: Warning
    Message: fsockopen() [function.fsockopen]: SSL operation failed with code 1. OpenSSL Error messages: error:140770FC:SSL routines:func(119):reason(252)
    Filename: libraries/Email.php
    Line Number: 1641

I don&#39;t want to use phpmailer now. (Actually I have tried to use phpmailer, but I failed).

How do I solve this problem guys?

Sending email with gmail smtp with codeigniter email library

How many characters are allowed to be in the subject line of Internet email?
I had a scan of [The RFC for email][1] but could not see specifically how long it was allowed to be.
I have a colleague that wants to programmatically validate for it.

If there is no formal limit, what is a good length in practice to suggest?


  [1]: http://www.w3.org/Protocols/rfc822/

What is the email subject length limit?

is there anyway that I can use &quot;mailto&quot; with empty recipient? I only want to supply the subject and the message body and then the user can write the to addresses on mail. I tried writing only a space but it didn&#39;t work.


mailto with empty recipient?

I use [TinyMCE][1] to allow minimal formatting of text within my site. From the HTML that&#39;s produced, I&#39;d like to convert it to plain text for e-mail. I&#39;ve been using a class called [html2text][2], but it&#39;s really lacking in UTF-8 support, among other things. I do, however, like that it maps certain HTML tags to plain text formatting — like putting underscores around text that previously had &amp;lt;i&amp;gt; tags in the HTML.

Does anyone use a similar approach to converting HTML to plain text in PHP? And if so: Do you recommend any third-party classes that I can use? Or how do you best tackle this issue?

  [1]: http://tinymce.moxiecode.com/
  [2]: http://www.chuggnutt.com/html2text.php

Converting HTML to plain text in PHP for e-mail

I am trying to do an SQL query, but I need to check somehow if the value is an email address.
I need a way to check if `$user` is an email address, because I have user values such as this in my table.

    test
    test2
    test@example.com
    test2@example.com
    test392
    test@example.net

and so on...


**I need to make it so `$useremail` checks `$user` to find if it&#39;s an email address. So I can UPDATE the values, `WHERE user=test OR user=test@example.com`, etc.**

    $user = strtolower($olduser);
    $useremail = &quot;&quot;;

    mysql_query(&quot;UPDATE _$setprofile SET user=$sn, fc=$fc WHERE user=&#39;$user&#39; OR user=&#39;$useremail&quot;);



Check if a string is an email address in PHP

What&#39;s a good technique for validating an e-mail address (e.g. from a user input field) in Android? [org.apache.commons.validator.routines.EmailValidator][1] doesn&#39;t seem to be available. Are there any other libraries doing this which are included in Android already or would I have to use RegExp?


  [1]: http://commons.apache.org/validator/apidocs/org/apache/commons/validator/routines/EmailValidator.html

How should I validate an e-mail address?

I&#39;m not asking about full email validation.

I just want to know what are allowed characters in `user-name` and `server` parts of email address. This may be oversimplified, maybe email adresses can take other forms, but I don&#39;t care. I&#39;m asking about only this simple form: `user-name@server` (e.g. wild.wezyr@best-server-ever.com) and allowed characters in both parts.

What characters are allowed in an email address?

I&#39;m not too sure how to do this.  I need to validate email addresses using regex with something like this:

    [a-z0-9!#$%&amp;&#39;*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&amp;&#39;*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+(?:[A-Z]{2}|com|org|net|edu|gov|mil|biz|info|mobi|name|aero|asia|jobs|museum)

Then I need to run this in a jQuery function like this:   

    $j(&quot;#fld_emailaddress&quot;).live(&#39;change&#39;,function() { 
    var emailaddress = $j(&quot;#fld_emailaddress&quot;).val();
    
    // validation here? 
    
    if(emailaddress){}
    
    // end validation
    
    $j.ajax({  
            type: &quot;POST&quot;,  
             url: &quot;../ff-admin/ff-register/ff-user-check.php&quot;,  
            data: &quot;fld_emailaddress=&quot;+ emailaddress,  
            success: function(msg)
            { 
    			if(msg == &#39;OK&#39;) { 
    			$j(&quot;#fld_username&quot;).attr(&#39;disabled&#39;,false); 
    			$j(&quot;#fld_password&quot;).attr(&#39;disabled&#39;,false); 
    			$j(&quot;#cmd_register_submit&quot;).attr(&#39;disabled&#39;,false); 
    			$j(&quot;#fld_emailaddress&quot;).removeClass(&#39;object_error&#39;); // if necessary
    			$j(&quot;#fld_emailaddress&quot;).addClass(&quot;object_ok&quot;);
    			$j(&#39;#email_ac&#39;).html(&#39;&amp;nbsp;&lt;img src=&quot;img/cool.png&quot; align=&quot;absmiddle&quot;&gt; &lt;font color=&quot;Green&quot;&gt; Your email &lt;strong&gt;&#39;+ emailaddress+&#39;&lt;/strong&gt; is OK.&lt;/font&gt;  &#39;);
    			} else {  
    			$j(&quot;#fld_username&quot;).attr(&#39;disabled&#39;,true); 
    			$j(&quot;#fld_password&quot;).attr(&#39;disabled&#39;,true); 
    			$j(&quot;#cmd_register_submit&quot;).attr(&#39;disabled&#39;,true);  
    			$j(&quot;#fld_emailaddress&quot;).removeClass(&#39;object_ok&#39;); // if necessary
    			$j(&quot;#fld_emailaddress&quot;).addClass(&quot;object_error&quot;);
    			$j(&#39;#email_ac&#39;).html(msg);
    			}
            }
    	 });
    });

Where does the validation go and what is the expression?

Validating email addresses using jQuery and regex

&gt; **Possible Duplicate:**  
&gt; [Best practices for validating email address in Objective-C on iOS 2.0?](https://stackoverflow.com/questions/800123/best-practices-for-validating-email-address-in-objective-c-on-ios-2-0)  

&lt;!-- End of automatically inserted text --&gt;

I am developing an iPhone application where I need the user to give his email address at login.

What is the best way to check if an email address is a valid email address?


Content Type	Original Author	Original Content on Stackoverflow
Question	David Watson	View Question on Stackoverflow
Solution 1 - Validation	user151323	View Answer on Stackoverflow
Solution 2 - Validation	Mark	View Answer on Stackoverflow
Solution 3 - Validation	Josh Stodola	View Answer on Stackoverflow
Solution 4 - Validation	Lars Munkholm	View Answer on Stackoverflow

What is the actual minimum length of an email address as defined by the IETF?

Validation Problem Overview

Validation Solutions

Solution 1 - Validation

Solution 2 - Validation

Solution 3 - Validation

Solution 4 - Validation

sem_init on OS X

To get total number of columns in a table in sql

Attributions