What the message looks like
550 5.7.0 Rejected by spam filter554 5.7.0 Reject, id=12345 - spam550-5.7.0 Message considered as spam or virus, rejected552-5.7.0 This message was blocked because its content presents a potential security issue
What it means
The receiving server's filters decided the email was spam, or that its content wasn't safe, and refused it. The standard name for this status is "other or undefined security status", so the wording after the code usually gives the real reason.
The temporary version, 421 4.7.0, asks the sender to try again later.
Common causes
- The content looks like spam, such as lots of links, a short message with a link, or phrases common in scams.
- The sending server or domain has a poor reputation, or is on a blocklist.
- An attachment type the receiver blocks, such as
.exe,.jsor older Office files with macros. Gmail's "potential security issue" message means this. - The email failed SPF, DKIM or DMARC checks, which counts heavily against it.
If you're the recipient
Add the sender to your contacts or safe senders list, and ask your provider's support about the rejection if a sender you want keeps being blocked. Some providers let you turn down their spam filtering.
If you're the sender
Check your domain's SPF, DKIM and DMARC, and whether your sending IP is on a blocklist. For attachments, send the file in a different format or share it with a link instead. If you send marketing email, only email people who asked for it.
If you use addy.io
If your inbox provider rejects an email that addy.io forwards to you as spam, it appears on your Failed Deliveries page. Adding the alias to your contacts, encrypting forwarded emails or replacing the subject can help. See I'm not receiving any emails, what's wrong?