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IDProjectCategoryView StatusLast Update
0001758SOGoWeb Calendarpublic2022-11-09 11:07
Reportergazda Assigned To 
Status newResolutionopen 
Product Version1.3.14 
Summary0001758: Cannot import an .ics with binary attachment

I cannot import the attached file using SOGo web client. It works when it I manually remove all ATTACH attributes. Is there something wrong with the file itself? I do not see any error message either in the SOGo backend log or in the web client. Web client simply says "No event was imported". I found no way to find out what is wrong with the file.

TagsNo tags attached.


2012-04-05 13:21


outlook.ics (308,031 bytes)
Christian Mack

Christian Mack

2012-04-10 12:14

developer   ~0003701

Last edited: 2012-04-10 12:19

Binary attachments are not supported for events or tasks in SOGo, nor Thunderbird/Lightning.
You only can attach URLs to a file, not the file itself.

The iCalendar standard allows but discourages the use of binary attachments.
RFC 2445:
" ...
4.1.3 Binary Content

Binary content information in an iCalendar object SHOULD be
referenced using a URI within a property value. That is the binary
content information SHOULD be placed in an external MIME entity that
can be referenced by a URI from within the iCalendar object. In
applications where this is not feasible, binary content information
can be included within an iCalendar object, but only after first
encoding it into text using the "BASE64" encoding method defined in
[RFC 2045]. Inline binary contact SHOULD only be used in applications
whose special circumstances demand that an iCalendar object be
expressed as a single entity. A property containing inline binary
content information MUST specify the "ENCODING" property parameter.
Binary content information placed external to the iCalendar object
MUST be referenced by a uniform resource identifier (URI).

The following example specifies an "ATTACH" property that references
an attachment external to the iCalendar object with a URI reference:


The following example specifies an "ATTACH" property with inline
binary encoded content information:

    <...remainder of "BASE64" encoded binary data...>


Are you sure you want all sorts of files on your calendar server?

I don't, because of the following reasons:
1) Binary data in an event is synchronised via CalDAV with the event as one object. So every client has to download it, before displaying the event.
1a) Even people who never look at this file have to download it.
1b) It also goes to every Smartphone connected to this calendar.
1c) Every change (e.g. a new note, date or subject) to your event triggers a complete download on every client for it.
1d) Every client has to hold all binary data from all events of an calendar (or at least a period of time) in his memory when displaying events.

2) The calendar server has to handle the additional bandwidth and storage for these files.

3) You can't scan these files for viruses on the calendar server. Spreading malicious content will be hard to prevent.



2012-04-10 13:04

reporter   ~0003705

Thanks for your detailed reply, Christian.

Binary attachments are not supported for events or tasks
in SOGo, nor Thunderbird/Lightning.

I am fine with the fact, that SOGo does not support binary attachments - at least now, when I know it. It would be nice if SOGo itself could tell me that that it does not support binary attachments when I try to import one. And it would be nice if SOGo would offer me an option to strip/ignore the binary attachments or even better, an option to detach/save the binary attachments on import.

The attached .ics file comes from an external site. It is a an invitation to a training and the attachment is a PDF registration form. Is there a way how my users could simply extract those forms out of the invitation?

Thanks again,


Christian Mack

Christian Mack

2012-04-10 13:56

developer   ~0003707

Sorry, but I don't know an easy way to extract it.

I could do it manually, by copying the base64 part, decode it and save it as PDF file.
But that's not what an end user would do.



2012-04-10 15:12

reporter   ~0003708

Thanks again for your prompt reply, Christian.

Sorry, but I don't know an easy way to extract it.

I could do it manually, by copying the base64 part,
decode it and save it as PDF file.
But that's not what an end user would do.

OK, I accept your reply for extracting/detaching.

But how about informing the user that binary attachments are not supported when he tries to import one?
And how about opting the user for ignoring the the binary part?



Christian Mack

Christian Mack

2012-04-10 16:31

developer   ~0003710

Because of these open issue I changed this bug report to an enhancement request.
There should be a way in order to handle binary attachments.



2015-09-01 11:54

reporter   ~0008882


A better way to do that as binary attachment is not recommended, would be to support extra linking on external storage like filelink do for email large attachments (

It would be nice to have into SOGo (and lightning) a button "attach file". When user "attach" : app uploads file via filelink and add url attachment in task or event.

What do you think about that? Is it easily possible? It would be a very very important and expected new feature, isn't it?

Best regards,




2016-07-15 19:01

reporter   ~0010499

afaik this is "by design":

RFC 2445

ATTACHMENTS - An iCalendar object can include references to Uniform Resource Locators that can be programmed resources.

No mentions about binary attachments, just URL...



2022-11-09 11:07

reporter   ~0016358

In order to support ActiveSync (EAS) 6.0 and higher, calendar attachments should be supported.


Issue History

Date Modified Username Field Change
2012-04-05 13:21 gazda New Issue
2012-04-05 13:21 gazda File Added: outlook.ics
2012-04-10 12:14 Christian Mack Note Added: 0003701
2012-04-10 12:19 Christian Mack Note Edited: 0003701
2012-04-10 13:04 gazda Note Added: 0003705
2012-04-10 13:48 Christian Mack Severity major => feature
2012-04-10 13:56 Christian Mack Note Added: 0003707
2012-04-10 15:12 gazda Note Added: 0003708
2012-04-10 16:31 Christian Mack Note Added: 0003710
2015-09-01 11:54 thierry Note Added: 0008882
2016-07-15 19:01 peterbeck Note Added: 0010499
2022-11-09 11:07 evert_mouw Note Added: 0016358