Email forwarding generally refers to the re-sending of email messages sent to one email address to different possible email addresses.
The term forwarding has no special technical meaning, but it implies that the email has moved "forward" to the new destination.
Email forwarding can also point an email to a specific address and send it to one or more other addresses. Similarly, vice versa, email items sent to multiple different addresses can be unified via forwarding to end in a single address in the box.
Email users and email system administrators use the same terms when talking about server-based and client-based forwarding.
Video Email forwarding
Server-based forwarding
The domain name (the section that appears to the right of @ in the email address) defines the target server for the corresponding address class. A domain can also define a backup server; they do not have mailboxes and forward messages without changing any part of their envelopes. Instead, the primary server can send messages to user mailboxes and/or forward by changing some envelope addresses. ~/.forward files (see below) provides a typical example of server-based forwarding to different recipients.
Email administrators sometimes use the term redirection as a synonym for server-based email forwarding to different recipients. The protocol engineer sometimes uses the term Mediator to refer to the forwarding server.
Due to spam, it's harder to forward emails to different domains, and some advise to avoid them if possible.
Use server-based forwarding to different recipients
- Role-addressesÃ,
- info , sales , postmaster , and similar names can appear on the left @ at the email address. Organizations may forward messages designated for specific roles to the personal addresses of persons functioning in such roles or offices.
- Vanity-addressÃ,
- Most domain name hosting facilities provide email facilities for forwarding emails to other email addresses such as Internet Service Provider users.
- Dissolved Address
- When users change their email address, the administrator can set forward from the old address to the old address in order not to lose the message.
Forwarding versus remailing
Delivery plain messages change the envelope recipient and leave the envelope sender field untouched. The "envelope sender" column is not the same as the From header typically shown by Email software: it represents the field used in the early stages of the SMTP protocol, and then saved as Returns -Path . This field contains the address to which the mail system should send bounce messages - reporting delivery failure (or success) - if any.
Conversely, the term remailing or redistribution can sometimes mean re-sending messages and also rewriting the "envelope sender" field. Electronic mailing lists provide a typical example. The author sends a message to the reflector that does the remailing to each address list. That way, bounce messages (which report the failure of sending messages to each subscriber list) will not reach the author of the message. However, the annoying autoreplies vacation failed to reach the author.
Usually, the delivery of plain messages extends aliases, while forwarding the right messages, also called forwarding tout-court works for mailing-mailing lists. When additional modifications to the message are made, making it more like the Mail User Agent action that sends new messages, the term forwarding becomes deceptive and re-makes it seem more appropriate.
In Sender Policy Framework (SPF), the domain name in the envelope sender remains subject to policy restrictions. Therefore, SPF generally prohibits the sending of regular messages. The Intra domain redirection complies with the SPF as long as the relevant server shares a consistent configuration. Email servers that practice forwarding of inter-domain messages can damage SPF even if they do not apply their own SPF, ie they do not apply SPF checks or publish SPF records. Sender Rewriting Scheme provides a common forwarding mechanism compatible with SPF.
Maps Email forwarding
Client-based forwarding
Automatic client-based forwarding
Client forwarding can be done automatically using non-interactive clients such as email retrieval agencies. Although the retrieval agent uses a client protocol, this forwarding resembles server forwarding as it preserves the identities of the same message. Concerns about envelope senders apply.
Forwarding client-based manuals
End users can manually forward messages using an email client. Forwarding inline quotes messages under the main text of new messages, and usually retains the original attachments as well as selected header options (eg the original From and Reply-To .) The recipient of a message forwarded in this way may still be able to reply to the original message; the ability to do so depends on the existence of the original header and can manually imply copying and pasting the relevant destination address.
Forward as an attachment prepares an MIME (message type/rfc822 attachment) containing the original full message, including any headers and attachments. Note that including all headers reveals a lot of information about the message, such as the server that sent it and every client tag added to the mailbox. Recipients of messages forwarded in this way may be able to open the attached message and respond in fluently.
This kind of forwarding is actually a remailing from the point of view of the sender of the envelope and the receiver. The identity of the message also changes.
Historical development of email forwarding
RFC 821, Simple Mail Transfer Protocol , by Jonathan B. Postel in 1982, is provided for forward-path for each recipient, in the form, for example, @ USC -ISIE.ARPA, @ USC-ISIF.ARPA: Q-Smith@ISI-VAXA.ARPA - a list of preferred host and destination mailboxes. When the host list exists, it serves as a route-source, indicating that each host must deliver a letter to the next host on the list. Otherwise, in the case of insufficient destination information but where the server knows the correct destination, it can take responsibility for delivering the message by responding as follows:
S: RCPT TO: & lt; Postel@USC-ISI.ARPA> Â Â Â Â Â R: 251 Non-local user; will forward to & lt; Postel@USC-ISIF.ARPA>
The concept at the time imagines elements from forward-path (source route) move to return-path (envelope sender) as messages forwarded from one SMTP server to another. Even if the system does not allow the use of source-routing, dynamically building a return-path implies that the envelope sender information can not remain in its original form during the forwarding process. So RFC 821 did not initially allow normal forwarding messages.
The introduction of MX records makes source routing unnecessary. In 1989, RFC 1123 recommended accepting source routing only for backward compatibility. At that point, regular message delivery becomes the recommended action for alias expansion. In 2008, RFC 5321 still mentions that "the system may remove the path back and rebuild it as needed", taking into account that not doing so may inadvertently disclose information sensitive. In fact, plain-forwarding messages can be easily used for alias expansion in the same server or a set of coordinated servers.
~/.forward file
sendmail, a reference SMTP implementation in the early 1980s, is provided for the ~/.forward file, which can store the target email address for a given user. This type of server-based forwarding is sometimes called dot-forwarding . One can configure multiple email-program filters to automatically forward or respond to actions immediately upon receipt. Files that are forwarded can also contain shell scripts, which have been the source of many security issues. Previously only trusted users can use the command line switch to set envelope senders, -f arg ; some systems disable this feature for security reasons.
Email preceded the formalization of client-server architecture in the 1990s. Therefore, the differences between client and server seem to need to be forced. The original contrast of daemon and user-controlled programs run on the same machine. The sendmail daemon is used to execute root privileges so that it can replicate all users whose emails should be managed. On the other hand, users can access their mail files and configuration files, including ~/.forward . Client programs can assist in editing server configuration files from specific users, thus causing confusion about what role each program plays.
Virtual users
The term "virtual users" refers to email users who never log on to the email server system and only access their mailboxes using remote clients. Mail-server programs can work for virtual and regular users, or may require slight modifications to take advantage of the fact that virtual users often share the same system id . The latter state allows the server program to implement some features more easily, as it does not have to comply with system-access restrictions. The same operating principle applies. However, virtual users have more difficulty in accessing their configuration files, good or bad.
See also
- Grouped email
- Electronic mailing list
- Aliases â € <â €
- Email Letter
- Email subject abbreviation
- Spam email
- Mail user agent (MUA) email client a.k.a.
- Message transfer agent (MTA)
- Reply All
Note
Source of the article : Wikipedia
0 Comments