Web.de
Web.de is a search engine and email provider, headquartered in Germany. Eurproean receivers tend to have high expectations for GDPR legal complaince, and in some cases email deliverability is aided when the sender is included in high profile "whitelists" and certification programs.
10 responses across 1 reply codes
SMTP 550
10 responses
1
Web.de rejected this because SPF failed for the sending IP. Publish a correct SPF record that includes your sending servers.
2
Web.de refused reception due to incorrect server configuration. Fix SMTP setup with your admin, then retry.
3
Web.de says the mailbox is unavailable. It may not exist or may be disabled for inactivity. Verify, then suppress if it stays dead.
4
Web.de rejected your IP for a bad PTR record. Set a proper reverse DNS hostname for the sending IP, then resend.
5
Web.de rejected the message for header policy problems. Fix Date, From, Sender, and To headers so they are unique and RFC-valid.
6
Web.de rejected the sender domain under security policy. Improve domain reputation before sending again.
7
Web.de temporarily blocked your IP after too much spam-like traffic. Pause volume and clean engagement before retrying.
8
This Web.de mailbox is over quota. Retry later, or ask the recipient to free space.
9
Your IP is on a block list used by Web.de. Delist it, then retry after caches refresh.
10
Web.de could not find a valid MX or A record for your domain. Publish working mail DNS so replies and bounces can land.
Response catalog adapted from the MIT-licensed SMTP Field Manual by ActiveCampaign / Postmark.