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linux:email [2019/01/21 11:27] (current)
seanburns created
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 +<​markdown>​
 +# Email basics
 +## Wed 28 Nov 2018 
  
 +## Historical influences
 +
 +Email was originally based very much on the office memorandum, which is
 +structured with fields like so:
 +
 +- To:
 +- From:
 +- Date:
 +- Subject:
 +- Content (DATA)
 +
 +## Email servers and clients
 +
 +1. Store and forward
 +    - messages are stored and forwarded when appropriate
 +2. Email servers ​
 +    - accept, forward, deliver, store messages
 +3. Email clients
 +    - connect to email servers to send messages or retrieve messages
 +
 +- MUA, mail user agent. From email client to:
 +- MSA, mail submission agent. The SMTP server does a:
 +- DNS server lookup. From DNS to:
 +- MTA, mail transfer agent. The SMTP server to:
 +- Remote server. The remote server:
 +- MDA, mail deliver agent to remote mailbox.
 +- MUA, mail user agent, reads email.
 +
 +## Email headers
 +
 +See RFC 5322: https://​tools.ietf.org/​html/​rfc5322
 +
 +Some important headers:
 +
 +### Originator fields
 +
 +These three could be the same or different:
 +
 +- from: the author of the message
 +- sender: the person sending the message
 +- reply-to: reply messages sent to this person
 +
 +### Destination address fields
 +
 +- to: the primary recipient
 +- cc: (carbon copy), secondary recipients
 +- bcc: (blind carbon copy), multiple uses
 +
 +### Identification fields
 +
 +- message-id: a unique identifer
 +- in-reply-to:​ a unique follow up identifier
 +
 +### Informational fields (human readable)
 +
 +- subject: ​
 +- comments:
 +- keywords: ​
 +
 +Important comment on "​Re:",​ Latin for "In the matter of" -- this is application
 +dependent and not required.
 +
 +## Message body / Data
 +
 +- ASCII, American Standard Code for Information Interchange:​ character encoding
 +- MIME, Multipurpose Internet Mail Extensions
 +    - non-ASCII text
 +    - non-text
 +    - and more
 +
 +MIME file (~/​.mailcap) on my system:
 +
 +```
 +image/*; eog '​%s'​
 +text/html; w3m -I %{charset} -T text/html; copiousoutput;​
 +audio/*; cvlc '​%s'​
 +#​application/​pdf;​ evince '​%s'​
 +application/​pdf;​ mupdf '​%s'​
 +application/​force-download;​ evince '​%s'​
 +application/​x-msword;​ soffice --nologo --writer '​%s'​
 +```
 +
 +## Email Security
 +
 +Some issues:
 +
 +- Spam
 +- Malware
 +- Phishing
 +- Spoofing
 +- Privacy
 +    - lack of encryption
 +    - intermediate systems
 +    - storage issues on remote systems
 +    - metadata
 +</​markdown>​
linux/email.txt ยท Last modified: 2019/01/21 11:27 by seanburns