BT 10mb to 25mb
This size limit applies to all messages (inbound, outbound, and internal) and can't be amended. The default attachment size limit for a single attachment is 10MB. Messages larger than 25MB will not be delivered, and the sender will receive a Non- Delivery Report

Yahoo 25mb
The sum of all attached files in a single message, both for incoming and outgoing email, must not exceed 25MB in total file size. Was this article helpful?

Gmail 25mb
Attachment size limit
You can send up to 25 MB in attachments. If you have more than one attachment, they can't add up to more than 25 MB. If your file is greater than 25 MB, Gmail automatically adds a Google Drive link in the email instead of including it as an attachment.

AOL 25mb
Whether you're sending cute baby pictures, or attaching a copy of your favourite recipe, AOL Mail lets you send and receive all kinds of email attachments. File names can't include special characters. The total file size is limited to 25MB per email, which includes both incoming and outgoing messages. 1.21 Nov 2019

Outlook.com 34mb
What is the Outlook attachment size limit? Sadly, due to mail server restrictions, the default max attachment size limit of files attached in Outlook is 20 megabytes (MB). This attachment limit applies to both Outlook and Office 365 versions of Outlook.

Live
10Gb storage (per email) and no more than 50Mb per file attached