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123 lines
4.7 KiB
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123 lines
4.7 KiB
Plaintext
#!/bin/cat
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$Id: FAQ.Dates.txt,v 1.11 2019/12/23 12:46:50 gilles Exp gilles $
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This documentation is also available online at
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https://imapsync.lamiral.info/FAQ.d/
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https://imapsync.lamiral.info/FAQ.d/FAQ.Dates.txt
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=======================================================================
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Imapsync tips about dates.
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=======================================================================
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Questions answered in this FAQ are:
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Q. We have found that the time and date displayed have been changed to
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the time at which the file was synchronized. What happened? Any fix?
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Q. Is there a way to set any message with
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"Date: (Invalid)" to a valid one like
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"Date: Thu, 1 Jun 2017 23:59:59 +0000"?
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=======================================================================
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Q. We have found that the time and date displayed have been changed to
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the time at which the file was synchronized. What happened? Any fix?
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R. This is the case by default with some email readers like:
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- Outlook 2003
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- Ipad
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- Iphone
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- spark https://sparkmailapp.com/ (iphone app)
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- Edison mail https://apps.apple.com/us/app/email-edison-mail/id922793622 (iphone app)
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- ...
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but not with:
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- Mutt
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- Thunderbird
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- Zimbra
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- Gmail
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First, a thing to keep in mind.
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Imapsync does not touch any byte of messages unless told to do so by
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special and rarely used options like --regexmess or --pipemess.
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Messages on both parts should be exactly identical because imapsync
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does a verbatim sync of all messages, by default.
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Now I explain the whole picture about dates of messages.
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There are several different dates attached to any message.
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First, there is the "Date:" header, which belongs to the message itself.
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You can see this "Date:" header line by asking "View->Message Source"
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in most email client software (Ctrl-u in Thunderbird).
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Most of the time, this "Date:" header date is set by the MUA,
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MUA stands for "Mail User Agent".
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MUA can be Outlook, Thunderbird, a webmail or Mutt etc.
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The "Date:" header is usually the date the message was written
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or sent the first time, at the writer side.
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This "Date:" header line is never changed by any transfer or copy.
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If an email reader uses the "Date:" header for displaying the date of
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a message then no problem should arise.
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Another date is the "internal date". In IMAP, the internal date is
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handled by the imap server and normally it corresponds to the arrival
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date in the mailbox. This date is not part of the email message
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itself, it is a metadata kept by the imap server.
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The IMAP protocol allows the internal date to be set by an email client
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when a message is delivered by the imap APPEND command.
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Imapsync synchronizes these internal dates, by default, so internal dates
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on host2 should then be the same as the internal dates on host1.
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If an email reader uses the internal date for displaying the date of a
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message then the sync date problem only occurs when the host2 imap
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server ignores the internal date given by imapsync during the APPEND
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imap command. It happens with some imap servers. Bad luck.
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There are also the "Received:" header lines. Each time a message
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travels a SMTP server, this one adds a "Received:" header
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line. Sometimes some email clients use the last "Received:" header
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date as the date of the message. And some IMAP servers software add a
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"Received:" line after and imap transfer. If those both conditions are
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met then the date displayed become the transfer date even if imapsync
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has done its best to keep all the dates synchronized. Bad luck.
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Solutions:
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a) Use another email client or configure it in order that it sorts messages
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by sent dates, the "Date:" header line.
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b) Use a imap server that respects the imap RFC and accepts
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the internal date set by imapsync.
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c) Try to understand why the email client software shows another date
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than the "Date:" header line.
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=======================================================================
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Q. Is there a way to set any message with
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"Date: (Invalid)" to a valid one like
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"Date: Thu, 1 Jun 2017 23:59:59 +0000"?
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R. Yes, there is a way with option --regexmess
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First, let's select only messages with a buggy Date header:
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--search "HEADER Date Invalid"
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Second, let's change this line by a valid one,
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on windows:
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--regexmess "s{\A(.*?(?! ^$))^Date:\ \(Invalid\)(.*?)$}{$1Date: Thu, 1 Jun 2017 23:59:59 +0000}xms"
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on Unix (replaced enclosing double-quotes " by single quotes ' ):
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--regexmess 's{\A(.*?(?! ^$))^Date:\ \(Invalid\)(.*?)$}{$1Date: Thu, 1 Jun 2017 23:59:59 +0000}xms'
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=======================================================================
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=======================================================================
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