Email refused for a line that is too long

A sender, or your own script, gets a refusal from Mailyoto that says a line is too long. The exact wording depends on where in the message the long line sits.

Why it happens#

Mail servers send email as lines of text, and the email standard limits how long one line may be. Mailyoto accepts lines of up to 65,536 bytes, far more than the standard asks for, and refuses a message with a longer line.

A line that long almost always comes from software that writes a whole HTML email, or a whole attachment, as one line without encoding it. Mail apps encode their messages correctly. This is rare from a person writing an email.

Other mail servers can enforce the standard’s shorter limit. A long line can then fail at a destination even after Mailyoto accepts it.

Fix it#

The sending software causes the long line, and whoever runs it fixes it.

1. Encode the message body#

   Set the body’s transfer encoding to quoted-printable or base64. Both break the content into short lines and restore it at the other end. Most email libraries have a setting for it.

2. Encode attachments#

   Attachments are always sent as base64, which keeps every line short.

3. Send the email again#

   Send the same message once the encoding is in place.

Confirm it worked#

The sending software gets a response that starts with 250. For a message to your alias, open Logs and find it with Delivered as its status.

The email comes from a website form or a shop

The form or shop software builds the message. Ask whoever runs it to turn on quoted-printable or base64 encoding for outgoing email.