SMTP error (550)

Hello,
I have this error : SMTP error (550) - 5.1.1 recipient adress rejected .
I receive all mails well but when I try to send, it’s impossible (with roundcube web and also with thunderbird with my MIAB parameters).
It’s making this error for 1 month, before, all was working well …
Any help please ?
box.xlib.ovh Webmail  Rédiger - Mozilla Firefox

I see the domain “free.fr” in your error message and this doesn’t look like what I would expect from a MIAB setup. Can you give me the MIAB hostname? On this error alone, I get the feeling you’ve overlapped with a different domain somehow

$ dig mx free.fr

; <<>> DiG 9.16.22-Debian <<>> mx free.fr
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 63512
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;free.fr. IN MX

;; ANSWER SECTION:
free.fr. 3600 IN MX 20 mx2.free.fr.
free.fr. 3600 IN MX 10 mx1.free.fr.

$ nslookup mx1.free.fr

Non-authoritative answer:
Name: mx1.free.fr
Address: 212.27.48.7
Name: mx1.free.fr
Address: 212.27.48.6

$ nslookup mx2.free.fr
Non-authoritative answer:
Name: mx2.free.fr
Address: 212.27.42.58
Name: mx2.free.fr
Address: 212.27.42.59

It’s the same with all the mail domains => I can’t send but receive well…
box.xlib.ovh Webmail  Rédiger - Mozilla Firefox_2
box.xlib.ovh Webmail  Rédiger - Mozilla Firefox

The error:

“SMTP error (550) - 5.1.1 recipient address rejected”

covers a lot of ground.

My first thought is that you are on a blacklist. Have you changed anything recently?

You are right : I am blacklisted
Network Tools DNS,IP,Email - Mozilla Firefox

I 've just made a request on Drone BL to remove my IP from blacklist…

I wouldn’t concern myself with UCEPROTECT.

I always check using DNSBL.info as they seem to check more lists than most other tools:

https://www.dnsbl.info/

Thanks for the link.
Results

I’m still waiting for my demand of removing IP on DroneBL

Also check /var/log/mail.log for responses from the other servers that are rejecting you. They often provide responses in the transaction messages.