Are there email attachment size limits?

Email sizes are limited to 25MB. Different email servers/systems have different size limits. There is no official standard, unfortunately, but the general rule is 10MB with most systems accepting up to 20MB. Our system accepts up to 25MB. This limit is not set by us but your ESP (email service provider.)
Due to the way that email works, the message size may exceed 25 MB even if the file attachment is smaller than that. This is because the attachment gets converted into a format that causes it to be bigger in size. An important thing to understand is that even if the file attachment is under the size limit, it will be expanded by up to 30% by your email program when it gets mailed.