220 themasterofyourdomain.com ESMTP service ready
250-themasterofyourdomain.com says hello
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250-8BITMIME
250-AUTH CRAM-MD5
250-AUTH=CRAM-MD5
250-XACK
250-SIZE 0
250-VERP
250 DSN

nginx

HTTP/1.1 200 OK
Server: nginx
Date: Sat, 02 Nov 2024 22:08:37 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Vary: Accept-Encoding
X-Frame-Options: SAMEORIGIN
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block

Squid http proxy4.15

HTTP/1.1 400 Bad Request
Server: squid/4.15
Mime-Version: 1.0
Date: Wed, 06 Nov 2024 18:32:34 GMT
Content-Type: text/html;charset=utf-8
Content-Length: 3482
X-Squid-Error: ERR_INVALID_URL 0
Vary: Accept-Language
Content-Language: en
Connection: close