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Email refused for being too large

The size limit Mailyoto applies to every email, the refusals a sender sees, and how to share large files instead.

Updated 27 October 2026

A sender, or your own mail app, gets one of these refusals from Mailyoto.

When the sending server announces the size in advance:

552 5.3.4 We take messages up to 52428800 bytes, and this one declares 70254592.

When the message goes over the limit during sending:

552 5.3.4 Error: Too much mail data

Why it happens#

Mailyoto accepts messages of up to 52,428,800 bytes, which is 50 MB. The same limit applies to email sent to your aliases and to email you send through Mailyoto SMTP.

The limit counts the whole message as it travels, not the files you attached. Email encodes attachments as base64, which makes each file about 37% larger. The files in one message can total about 36 MB.

Your destination inbox has its own size limit, which can be lower than Mailyoto’s. The destination can still refuse a message Mailyoto accepts. That refusal shows in your logs as Failed, with the destination’s response in Show details.

Fix it#

  1. Upload the files to a file-sharing or cloud storage service, and send the link in the email.

  2. Or split the attachments#

    Send the files across several emails, with under 36 MB of files in each.

  3. Send the email again#

    Send the smaller message.

Confirm it worked#

For a message to your alias, open Logs and find it with Delivered as its status. For a message you sent, your mail app shows no error, and the message is in its Sent folder.

I send through the API

The send endpoint of the Mailyoto API accepts at most 20 attachments, and the whole email up to 20 MB once encoded. Use links for anything larger.

Mailyoto accepted it, but the destination refused it

The destination’s limit is lower than the message. A link is the only way to get the file to that inbox.