If your subscriber list has over 1000 subscribers, then the maximum size of an email you may submit for distribution is 3MB.
That includes embedded images, attached files, etc. The reason is in the math: a 3MB message multiplied by 1000 copies sent to subscribers equals 3GB of email! A couple of messages of that size submitted by several customers within a few hours can quickly consume all the available working HDD space on our server.
The solution is simple: reduce the size of your message. Some possibilities:
- If you have embedded an image in the email, remove that and instead insert a LINK to the image, hosted on an image hosting site like Postimage.
- If you are sending an attachment, reduce its size.
- Consider putting the attachment on a website instead and just including a link to it in your newsletter. This has the added advantage of not forcing your recipients to each download an attachment which they may not need or want.
If your list has fewer than 1,000 subscribers, there is still a 5MB message size limit.