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Issue with attachments that seem to be increased in size RRS feed

  • Question

  • Good Morning, 

    We have a user who is telling us he is having issues attaching large files Outlook for MAC 2016. 

    We are an on-prem Exchange 2016 using cached mode. Our organizational limit for attachments is 55MB.  We also set our online mail OWA and EWS to be 55MB also. 

    Doing some testing, I attached a 20MB zip file, 10MB Zip file and 12MB pdf.  In outlook and OWA that sends as 42MB. 
    When I attach the same files into an email in the Outlook for MAC client.  The 20MB file now shows as 27MB, 10MB file is 13.5 and the 12MB file is 16.4.  That pushes it to 56.4, which is over our limit. 

    Get a message that reads: HTTP Error: Post data is too large, and the email is moved to the drafts folder. 
    Did same test with a 50MB zip file and it was in the email at 67MB.   Attached a 4MB MS Word document and it attached as 4MB. 

    This is not a limitation of the MS Exchange side, but only seems to happen in the Outlook for MAC Client. Not sure if it is handling .zip and .pdf files differently, unfortunately, do not have any MS office documents that large, and I don't have access to my IMac today for testing. 

    Has anyone seen this in the past. More looking for information, our Apple support team is also looking at it.  Trying to clear this one off my plate before vacation on Friday.

    Thank You


    Brian Dougherty

    Wednesday, August 21, 2019 12:04 PM

All replies

  • Size of the attachments increases depending on the encoding of that particular file. 

    The size is increased when the file is processed as an attachment that's suits the mail delivery, sometimes it even adds 30% more to the original file size.


    S_K_P

    Wednesday, August 21, 2019 10:37 PM
  • Hi Brian,

    According to my research, this is not a issue, this is the nature of email.

    Just as SKP said, you're not sending the original file, you're sending an encoded version of the file that can be anywhere from 20% to 60% larger than the original file.  It doesn't matter what size you see on the disk.  The size of the transmission will always be larger.

    Details: Email cannot send non-text information.  In order to accommodate non-text, designers of email systems added the ability to encode non-text files into text.  It's not human-readable, but it's text nonetheless.  This is called MIME (multipurpose internet mail extension).  Since text characters have fewer bits (six) of information in them than does binary characters (eight), any binary file encoded for transmission by email will grow in size.  On the receiving side, the mail client decodes the text characters back into their original binary form and the attachment size shrinks again.

    Hope this can be helpful.

    Regards,

    Aidan Wang


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.



    Thursday, August 22, 2019 1:48 AM
    Moderator
  • Thank you for the response.  I am curious why this only seems to happen on the Outlook for MAC client and not the Outlook client on Windows.   I will forward this onto my support teams looking at the issue. 

    Thursday, August 22, 2019 11:01 AM
  • Hi Brian,

    According to my test, this happen on both Outlook for Mac and Outlook for Windows.

    >>  I will forward this onto my support teams looking at the issue. 

    If there is any update, please feel free to share here.

    Regards,

    Aidan Wang


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Friday, August 23, 2019 7:12 AM
    Moderator
  • Hi Brian,

    I'm writing to see if the reply above is helpful to you. If yes, would you mind helping mark the reply as answer? So that others who might have a similar question can benefit from your thread? Thanks for your understanding and support.

    Regards,

    Aidan Wang


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.


    Monday, August 26, 2019 9:34 AM
    Moderator