Question

I read through a few pages but cannot understand how email sending works. What i know is, i can send an email using php mail() function. It connects to email server iteself and sends the email. It does not know whether the email actually reached the destination or not.

what i want to know is,

1. What is the role of MTA in all this, what does it do?

2. Can i use php mail() function to send emails to say 1000 people at once, without using any additional softwares on my server.

Answer 1

Role of MTA:

1. receives email from the client’s MUA
2. passes email to the MDA for final delivery
3. uses SMTP to route email between servers

See more: http://en.wikipedia.org/wiki/Message_transfer_agent

See this links for sending multiple emails:

1. Sending mass email using PHP
2. Sending bulk email in PHP

Update:

A message transfer agent(MTA) receives mail from either another MTA, a mail submission agent (MSA), or a mail user agent (MUA). The transmission details are specified by the Simple Mail Transfer Protocol (SMTP). When a recipient mailbox of a message is not hosted locally, the message is relayed, that is, forwarded to another MTA. Every time an MTA receives an email message, it adds a Received trace header field to the top of the header of the message, thereby building a sequential record of MTAs handling the message. The process of choosing a target MTA for the next hop is also described in SMTP, but can usually be overridden by configuring the MTA software with specific routes.

A MTA works in the background, while the user usually interacts directly with a mail user agent. One may distinguish initial submission as first passing through an MSA – port 587 is used for communication between an MUA and an MSA while port 25 is used for communication between MTAs, or from an MSA to an MTA; this distinction is first made in RFC 2476.