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140 lines
5.4 KiB
Plaintext
140 lines
5.4 KiB
Plaintext
#!/bin/cat
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$Id: FAQ.Messages_Too_Big.txt,v 1.8 2021/12/16 11:44:26 gilles Exp gilles $
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This document 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.Messages_Too_Big.txt
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=======================================================================
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Dealing with too big messages with Imapsync.
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=======================================================================
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Questions answered in this FAQ are:
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Q. Imapsync reports errors like these ones:
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"could not append...Maximum size of appendable message has been exceeded"
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"could not append...maximum message size exceeded"
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"The most frequent error is ERR_APPEND_SIZE"
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What does it mean?
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Q. Does imapsync limits big messages?
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Q. What are the well known servers messages size limits?
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Q. What can I do to transfer messages bigger than what allows the
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imap destination server?
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Q. The solution --truncmess xxxx doesn't work with Gmail.
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What can I do?
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Now the questions again with their answers.
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=======================================================================
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Q. Imapsync reports errors like these ones:
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"could not append...Maximum size of appendable message has been exceeded"
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"could not append...maximum message size exceeded"
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"The most frequent error is ERR_APPEND_SIZE"
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What does it mean?
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R. It means the message couldn't be transferred to the destination
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account because it is too big, imapsync tries to APPEND it to the
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server (that's IMAP jargon) but the server refuses it by saying
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either "NO. Maximum size of appendable message has been exceeded"
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or "NO. maximum message size exceeded".
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=======================================================================
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Q. Does imapsync limits big messages?
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R. No. Imapsync synchronizes messages no matter their sizes.
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When a message is copied to the destination server, the destination
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server accepts it or not. It does it as a whole, it takes the full
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message or nothing. The destination server can refuse a too big
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message, it then triggers an APPEND error message in imapsync.
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So far, December 2021, the biggest message transferred by imapsync on
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the online /X service is 1.51 GiB. Who can top that?
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=======================================================================
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Q. What are the well known servers messages size limits?
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* Gmail message size limit is 35 MB.
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Gmail announces APPENDLIMIT=35651584 (June 2021).
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* Office365 message size limit is 45 MB by default
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and it can be upped by configuration. See
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https://imapsync.lamiral.info/FAQ.d/FAQ.Office365.txt
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Q. I see "NO Maximum size of appendable message has been exceeded"
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* Exchange message size limit is 10 MB by default
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and it can be upped by configuration. See
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https://imapsync.lamiral.info/FAQ.d/FAQ.Exchange.txt
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Q. I see "NO Maximum size of appendable message has been exceeded"
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* Dovecot message size limit is variable. It is defined
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by the sysadmin. For example, quota_max_mail_size = 100M
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https://doc.dovecot.org/configuration_manual/quota/
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* Usually, any IMAP server has a message size limit, defined
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by the sysadmin. You discover it sooner or later
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=======================================================================
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Q. What can I do to transfer messages bigger than what allows the
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imap destination server?
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R1. A solution is ask imapsync to truncate the message to the maximum
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size allowed before copying it to host2 by using the option
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--truncmess.
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That's a little dirty but it's ok if you prefer having a truncated
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message than no message at all. The attachments after the truncation
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won't be available but everything before should be ok. It may also
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depend on the software tool reading the email message.
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To truncate messages to 10 MB, use:
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imapsync ... --truncmess 10_000_000
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R2. A not-so-dirty solution would be to transform the big messages,
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replace the attachments with links to the attachments stored
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elsewhere. Well, it's not done and it's too much complicated compared
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to a simpler solution which is to allow bigger messages on the
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destination account.
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As time goes on, disk space is cheaper and cheaper. Don't make the
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new user account, the destination account, worst than his previous
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account: buy disks.
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Monitor and rule your hardware resources, serve your users,
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not the contrary.
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=======================================================================
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Q. The solution --truncmess xxxx doesn't work with Gmail.
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What can I do?
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R. Gmail currently limits messages size up to 35651584 bytes, aka 34
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MiB (June 2021) but imapsync knows it so it avoid to transfer these
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big messages. Solution, use:
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imapsync ... --truncmess 35_651_584 --appendlimit 1_000_000_000_000
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Explanation. By default, imapsync checks if the host2 imap server
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announces a message size limit with "APPENDLIMIT=xxxx" in its
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CAPABILITY response, like Gmail does. Imapsync takes this APPENDLIMIT
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value to set automatically the --maxsize option, unless --maxsize is
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already set on the command line and has a smaller value than the
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APPENDLIMIT value.
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1_000_000_000_000 is one TB, I guess you don't have any message of
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that size yet.
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=======================================================================
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=======================================================================
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