SMTP error 553 5.7.1: sender address rejected

553 5.7.1 is a 5yz permanent failure paired with 5.7.1, the same security/policy enhanced

code used by the more commonly seen 550 5.7.1. The difference that matters is the base code and

*when* it fires: 553 rejects at the MAIL FROM stage, before any recipient has even been

specified, which means the server is refusing your claimed sender identity itself, not evaluating

the message or a specific recipient.

A real transcript

EHLO yourdomain.com
250 mx.example.com
MAIL FROM:<you@yourdomain.com>
553 5.7.1 Sender address rejected: not owned by user you@authenticated-account.com

The five "sender address rejected" messages

How the big three phrase it

Who is at fault

The sender, in essentially every case — this is a permanent rejection of your claimed identity,

not a content or reputation-only judgement. The two most common root causes are a

misconfigured relay permission (you are trying to send as an address your authenticated account is

not allowed to use) and a MAIL FROM domain that does not resolve in DNS at all.

Diagnose it yourself

1. Confirm the `MAIL FROM` domain resolves: dig MX yourdomain.com +short and `dig A

yourdomain.com +short` — a domain with neither record is a guaranteed rejection at this stage

for any receiver that checks.

1. Check what identity you actually authenticated as versus what you set in MAIL FROM — many

relays only allow authenticated users to send as their own address or a short allow-list, and

silently rejecting a mismatch is common.

1. Test the exact `MAIL FROM` value manually: `openssl s_client -starttls smtp -connect

mx.example.com:25, then issue EHLO, MAIL FROM:<exact-address>` by hand to isolate whether

the rejection is address-specific or affects every sender from your relay.

553 vs 550 vs 554: which rejection are you actually seeing

A 553 fires at MAIL FROM, before any recipient is known — the problem is your identity. A

550 5.7.1 usually fires at RCPT TO or DATA — the problem is this specific message or

recipient. A 554 is typically a whole-transaction permanent reject, often appearing right at

connection or EHLO. Which stage the rejection happens at is more diagnostic than the code itself.

How to fix 553 5.7.1

1. **Match your MAIL FROM to an address your authenticated account is actually permitted to send

as** — most relays only allow this for a verified, owned address.

1. Fix DNS for the sending domain if it does not resolve — a missing A or MX record on the

MAIL FROM domain is rejected by policy at many receivers regardless of anything else.

1. Authenticate before sending, if "Not logged in" is the specific message — confirm your

client is actually completing AUTH before MAIL FROM, not skipping it.

1. Request delisting if a reputation-list hit (like the Yahoo PBL example) is named in the

text — this is a different root cause from the other four and needs a blocklist-specific fix,

not a relay-permission fix.

What not to do

• Do not confuse this with 550 5.7.1 and apply content or recipient-side fixes — nothing about

the message body or the recipient address is relevant here, the rejection never got that far.

• Do not keep retrying with the same unauthorised MAIL FROM value — it is a permanent 5xx tied

to your identity, and it will fail identically every time until the identity or permission

changes.

• Do not add the mismatched address to your SPF record expecting that to fix it — SPF and relay

permission are separate mechanisms; SPF affects whether other receivers trust the domain, not

whether your own outbound relay will let you claim it.

MailPilot sends through each connected mailbox's own authenticated identity (OAuth for Gmail and

Outlook, SMTP credentials for SendGrid, SES, Mailgun, Postmark, and custom SMTP), so the

sender-identity mismatch behind most 553 5.7.1 rejections is not something warm-up traffic

through MailPilot can trigger.