UNIX 8 - E-Mail Applications Clients Run in user space...

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1 Electronic Mail Transport Agents CNIT 34000 – Lecture 8 E-Mail Applications Clients Run in user space Where the user composes and reads mail Get mail from incoming mail directory and send to outgoing mail queue Place outgoing mail in outgoing mail queue mail, elm, pine, etc. Transport Agents Run as daemons in the background Receive and send mail via SMTP Deliver and forward mail sendmail, qmail, postfix, smail, procmail MTA Mail Functionality Opens connections to remote machines to deliver mail via SMTP Monitors outgoing mail queue for mail to send Must be able to resolve DNS names Holds open SMTP (TCP 25) to receive mail /etc/host must contain incoming mail machine name Places mail in incoming mail queue for processing Parses incoming mail queue Delivers local mail to user’s mail directory Forwards mail addressed to local aliases Relays mail addressed to other machines Must be configured as a relay host Origin machine must be authorized MTA Naming Considerations A host that sends mail MUST have a valid hostname and fully qualified domain name The FQDN must be resolvable via DNS There can be multiple places to set the name – all must agree / MTA configuration files If you blow this you will end up blacklisted for being non- compliant If you will receive mail for anything other than the FQDN you must specify it in the /etc/hosts 172.16.5.45 hostname hostname.acme.com acme.com otherdomain.net MTA Mail Queues and Processing Incoming Mail Queue Where incoming messages are placed pending parsing and delivery/forwarding Outgoing Mail Queue Where local applications place messages that need to be sent Local Mail Delivery Location
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UNIX 8 - E-Mail Applications Clients Run in user space...

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