Increase Outlook 2010 Attachment Size

Most email providers limit the maximum size of attachments to a specific number, usually between five and 25 Megabytes. Companies like Microsoft have even started to offer workarounds by combining their email service (Hotmail) with offsite storage (Skydrive) to bypass attachment size limits.
Users of Microsoft Outlook 2010 may have noticed that the email client is not nearly as flexible when it comes to sending large file attachments. A limit of 20 Megabytes seems to have been hard coded into the email client. The settings do not offer any option to increase or decrease the attachment size limit.
Outlook 2010 users who try to add an attachment exceeding the 20 Megabyte limit receive a notification that "the attachment size exceeds the allowable limit". That could be a problem if the email provider supports larger attachment sizes. It is obviously possible to split the attachment but this would mean more work both for the sender and recipient as the attachments need to be split, and joined.

Most Outlook users do not know that it is possible to change the attachment size limit in the email program. The process requires manual editing of the Windows Registry, and it is recommended to create a system restore point or other form of backup before proceeding (see backup registry for pointers).
Open The Windows Registry editor by pressing Windows-R, typing regedit and the enter key in the end.
Navigate in the left Registry structure to the key
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences
Move the mouse to the right window over blank space and right-click there. This opens a context menu, select New > DWORD (32-bit) value from the list.
Name the new value MaximumAttachmentSize. Double-click the new parameter after it has been created and change the default value to another one. The new value has to be entered in Kilobytes. The easiest way to calculate the Kilobyte value is to multiple the Megabyte attachment size that you want, say 30, with 1024. You would in this case change to decimal in the window, and enter 30720 as the new value of the parameter to increase the attachment size limit to 30 Megabytes.
Setting the value to 0 removes the attachment size limit completely, which means that Outlook will try to send emails regardless of their size. Please note that this does not mean that they are accepted by the Internet Provider. (via NirmalTv)
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You said that Outlook isn’t your main email client, so which is your main one?
I think its thunderbird
It is Mozilla Thunderbird.
Awesome! This actually solved my problem… what a stupid bug.
If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.
THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!
Solved my issue! 6 years later and this is still problem…
Fantastic. Thank you. Size did the trick.
This solved my Outlook problem, too. Thank you. :)
Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.
You are a god – thank you!
thanks a lot…. work like charm.. :-)
Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers
Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
Thank you
Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)
Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.
I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!
Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007
Great tip! Thanks!
Worked for me, too – thank you!!!
It’s Worked for me, too
thank you very much!
I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!
Thank you so much. Solved!
Considering you published this in 2012, incredible not been debugged by Microsoft.
Thank you again. M
This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.
Thanks.
Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.
Thank you, this worked !!!!
Man, you are a fucking god. Thanks a lot, what an annoying bug!!
Awesome, this post solved the issue. Many thanks!