If you have an html code and would like to send directly from the editor, there is a security feature in Gmail that will prevent you to do this. To be able to send your email, you can copy the code and paste to a notepad or wordpad by removing the format. Then, you should be able to copy the newly formatted code, paste to Gmail email and send to your friend.

If you want to keep all your emails in one email account, you can do the following by choosing your gmail account:

1- Go to Settings section after loging to your gmail account.
2- Click on ‘Accounts and Import’
3- Click on ‘Import mail and contacts’
4- Enter your email address and password
5- Put an option to create a specific folder to organize your emails.

In  a few seconds, your other emails should start appearing in your Gmail account. The current process should work for Hotmail and Yahoo emails.

If you send a compressed file with the php or other codes in it, Gmail may reject the attachment due to security and attachment guidelines. You may receive the following message:

Your message did not reach some or all of the intended recipients.
Subject: Emailing: XXXX.zip Sent: 2/14/2010 1:15 PM
The following recipient(s) could not be reached: ‘XXXX XXXX’ on 2/14/2010 1:15 PM 552 5.7.0 review our attachment guidelines. 20sm5501368iwn.13

It apparently shows that the attachment was sent as a zip file. Gmail is able to check the content of the email if the attachment is compressed in zip format.

The solution of this is to send the same attachment as a rar format. Gmail is not able to check the content of the attachments compressed with WinRAR so, you should have no problem to transmitting the file to the recipient.