What's the maximum file size I can send as an attachment using BT Yahoo Mail?

The maximum email size is set at 25MB for your BT Yahoo! email account. However, you may find it hard to send attachments that are larger than about 20MB as attachments must be encoded so that other email programs can read them. Encoding attachments can add about 33% to their original size. So a 1.5MB attachment would be roughly 2MB after encoding.

If you need to send large files you can try these alternatives:


Zip up your files before you email them


Single or multiple files can be compressed with utility programs such as WinZip or Stuffit. Depending on the file, you can often reduce the file size a great deal.


Transferring files online


Using an online backup and storage site like BT Cloud is an easy way to share extremely large files with your family and friends.

BT Cloud comes free with BT Broadband. You can use BT Cloud to back up the bits of your digital life you choose. With BT Cloud, you get:

  • A secure, automatic backup
  • Your favourite files and photos on hand whenever you’re online
  • Access via PC, Mac, smartphone or tablet with our BT Cloud app
  • Content sharing with friends and family by email, Facebook and Twitter
  • Uploads wherever and whenever you need to free up space on your devices

To find out more, go to


Other services and tools


There are a variety of other services and tools that allow you to transfer extremely large files, up to 1Gb. Do a search on the web and you should be able to find one for free.

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