Does Zimbra support fetch message body in chunks, etc.?

[zzzzsg]

Dear Sir

When we receive an email with attachment and open the email in Thunderbird, Thunderbird always download the attachment when opening
the email.

Thinking that it may be a Thunderbird issue, we looked into Thunderbird
settings and found mail.imap.mime_parts_on_demand and mail.imap.fetch_by_chunks options which would supposedly resolve the
problem of downloading attachment when opening the mail, but they didn't.

Then we tested Thunderbird with a Sendmail/Imap-uw server and Thunderbird
did not download the attachment when opening the mail.

Questions --

1) Does Zimbra's IMAP server support 'fetching of message body in chunks'?

2) Does Zimbra's IMAP server support 'fetch only part of the body which will be displayed inline'?

Thank you.


The Thunderbird details.

http://kb.mozillazine.org/Entire_mes...a_IMAP_message


Found out this http://web.archive.org/web/200410241...9981005-3.html
mail.imap.fetch_by_chunks Bool true
Whether or not the client tries to fetch message bodies in chunks,if the server
supports it (IMAP4rev1). If false, it tries to fetch the whole body in a single
command.

mail.imap.mime_parts_on_demand Bool true
Whether or not the client will try to request the BODYSTRUCTURE for a message
when over a certain size threshold, and attempt to fetch only the parts of the
message that will be displayed inline. Some servers may not handle this
correctly (Exchange 5.5 may crash if pre-SP2), so turn this off as a workaround.

[dkarp]

These are all Thunderbird settings for how to fetch message attachments and the threshold size below which Thunderbird will auto-fetch attachments. They are independent of the IMAP server, and any differences you see are probably due to different test messages rather than to different IMAP servers.

Incidentally, we strongly suggest against fetching attachments by chunks. It's a huge waste of bandwidth to add the extra IMAP protocol chatter to do this, it has no real benefit to the user, and it hammers the Zimbra server's CPU if you're using a version before 4.5.3 and/or you have too small a zimbraMessageCacheSize.

[zzzzsg]

Dear dkarp

Thank you for the reply.

<< any differences you see are probably due to different test messages rather than to different IMAP servers >>

No, we tested with the same email messages with the same attachments.


I think others have also had this attachment download problem with Thunderbird/Zimbra.
IMAP emails with attachments slow to view

It is not Thunderbird's problem since Thunderbird has no problem with the Sendmail/imap-uw server.

According to Thunderbird's documentation, the IMAP server has to support the features
mail.imap.fetch_by_chunks and mail.imap.mime_parts_on_demand.
Thunderbird's document said that Exchange 5.5 has problem with the second feature.


Thank you.

Originally Posted by dkarp

These are all Thunderbird settings for how to fetch message attachments and the threshold size below which Thunderbird will auto-fetch attachments. They are independent of the IMAP server, and any differences you see are probably due to different test messages rather than to different IMAP servers.

Incidentally, we strongly suggest against fetching attachments by chunks. It's a huge waste of bandwidth to add the extra IMAP protocol chatter to do this, it has no real benefit to the user, and it hammers the Zimbra server's CPU if you're using a version before 4.5.3 and/or you have too small a zimbraMessageCacheSize.

[zzzzsg]

I think it is some settings on my Zimbra server (Zimbra 4.0.2) that causes this problem.

This is because I tested with another Zimbra server (Zimbra 4.5.3) and there was no problem of Thunderbird downloading the attachment when opening mail.

Is there anything on Zimbra 4.0.2 that can cause this problem? Or it is our server?

It is also not just Thunderbird.
The problem also happens in Eudora.

Thank you.

Originally Posted by dkarp

These are all Thunderbird settings for how to fetch message attachments and the threshold size below which Thunderbird will auto-fetch attachments. They are independent of the IMAP server, and any differences you see are probably due to different test messages rather than to different IMAP servers.

Incidentally, we strongly suggest against fetching attachments by chunks. It's a huge waste of bandwidth to add the extra IMAP protocol chatter to do this, it has no real benefit to the user, and it hammers the Zimbra server's CPU if you're using a version before 4.5.3 and/or you have too small a zimbraMessageCacheSize.

[dkarp]

Zimbra 4.5.3 added some extra caching to handle "fetch by chunks". If you're seeing slowdowns on IMAP download of large message attachments, an upgrade to 4.5.3 will probably help.

[zzzzsg]

Thanks dkarp

We just upgraded from 4.0.2 to 4.5.3, and yes, 4.5.3 fixed the Thunderbird's (and Eudora) problem of downloading attachment when opening mail.

Glad that Zimbra is getting better.

Originally Posted by dkarp

Zimbra 4.5.3 added some extra caching to handle "fetch by chunks". If you're seeing slowdowns on IMAP download of large message attachments, an upgrade to 4.5.3 will probably help.