Enhanced status code

SMTP error X.6.1

Media not supported

Updated Jul 1, 2026

The short answer

Media not supported Common cause: Receiver cannot process the message content type

Quick fix

Resend using supported MIME / content formats

This code is written X.6.1 because the reason is the same whether the failure is temporary (a 4 first digit) or permanent (a 5). Read the first digit of your own bounce to know which applies.

How to fix it

Resend using supported MIME / content formats

Related codes

X.6.0 Other or undefined media error X.6.2 Conversion required and prohibited X.6.3 Conversion required but unsupported X.6.4 Conversion with loss performed X.6.5 Conversion failed X.6.6 Message content not available
All SMTP error codes
Ready when you are

Most rejections come back to sender reputation.

Blocklists, auth failures, and policy blocks are what warmup prevents. Warm up your domain so your mail is trusted before you hit send.

Start 7-day free trial Book a demo
7-day free trialNo credit cardCancel anytime