Density is defined as how thick or thin you want your hair to be. The standard and most popular choice is 130% which is Medium Density. You can see examples of the density - Click Here.
Google's Gmail Web-based email service runs on the Internet Message Access Protocol system, but it also offers Post Office Protocol mail server access.
SMTP stands for Simple Mail Transfer Protocol. SMTP is used when email is delivered from an email client, such as Outlook Express, to an email server or when email is delivered from one email server to another. SMTP uses port 25. POP3 stands for Post Office Protocol. POP3 allows an email client to download an email from an email server. The POP3 protocol is simple and does not offer many features except for download.