📮 Strato mail limit debugger run-id: faad12

Ground truth check

Open ggabriella562jbg8@outlook.com at GMX and search for LIMTEST-faad12 (check spam folder too). The highest # that arrived per method = the real limit. mail() returning "OK" only means Strato's sendmail accepted it - delivery can still be dropped later, so the inbox count is what counts.

Important after a stop: re-count the inbox 1-2 hours later. Strato sometimes queues excess mail and delivers it late (trickle-in). If the count keeps growing, you are being throttled, not blocked.

1) Send test batch

DKIM key file: MISSING (upload dkim-private.key) | DNS record for s2026._domainkey: not found | SPF: missing | DMARC: v=DMARC1;p=reject;

Send to	(change to another mailbox you own! If mails arrive there but not at the GMX address, GMX is throttling hanna's inbox, not Strato blocking you)
Envelope From (Return-Path)	(envelope sender used by mail()/sendmail/relay/mx methods - test B-UADOM bypass: try any address on any domain, e.g. bounce@baumbua-bau.de)
Method	mail() [PHP classic -> Strato sendmail] mb_send_mail() [mbstring variant] imap_mail() [IMAP extension] sendmail binary [direct via popen] SMTP -> relay host [raw socket, e.g. smtp.strato.de] SMTP direct to MX [bypasses Strato completely] SMTP direct to MX + DKIM signed [THE BYPASS - needs dkim-private.key + DNS record]
How many per batch
Seconds between mails	(0 = as fast as possible; if you fail early try 2-5 to test burst vs hard limit)
Repeat batches	(auto-continues via page reload, keeps each HTTP request short)
SMTP relay settings (only for method "SMTP -> relay host")
Host
Port / TLS	STARTTLS (587)SSL (465)none / plain (25)
Mailbox login
Mailbox password
	🚀 Send batch

2) SMTP connectivity probe

Tests which SMTP channels are reachable from your webspace. "MAIL FROM ok without auth" = open relay from inside Strato (great for bypassing).

🔌 Run probe

3) Counters per method

Method	sent	OK	FAIL	limit detected at	last event
mail	15	10	5	10 (2026-10-26 13:38:30)	2026-10-26 13:38:30 FAIL #15 mail() returned false
mb_send_mail	5	0	5	0 (2026-10-26 13:39:17)	2026-10-26 13:39:17 FAIL #5 mb_send_mail() returned false
imap_mail	25	25	0	-	2026-10-26 13:39:34 OK #25

first failure ever seen per method: mail - 2026-10-26 13:38:30 (at #11: mail() returned false) | mb_send_mail - 2026-10-26 13:39:16 (at #1: mb_send_mail() returned false)

🔄 Reset counters (new run-id) 🔄 Reset counters + delete log

4) Environment (mail relevant)

PHP	8.2.35, SAPI cgi-fcgi
sendmail_path	/usr/sbin/sendmail -t -i
SMTP / smtp_port (win only)	localhost / 25
sendmail_from	(empty)
disable_functions	(none)
extensions	openssl=yes, mbstring=yes, imap=yes, sockets=NO
sendmail binaries	/usr/sbin/sendmail: exists, /usr/lib/sendmail: exists
host / ip	info / 82.165.86.87
sender / recipient	webmaster@baumbua-baumpflege.de -> ggabriella562jbg8@outlook.com

5) Log (last 300 lines)

[2026-10-26 13:38:25] mail         #1 OK   
[2026-10-26 13:38:25] mail         #2 OK   
[2026-10-26 13:38:25] mail         #3 OK   
[2026-10-26 13:38:26] mail         #4 OK   
[2026-10-26 13:38:27] mail         #5 OK   
[2026-10-26 13:38:28] mail         #6 OK   
[2026-10-26 13:38:28] mail         #7 OK   
[2026-10-26 13:38:29] mail         #8 OK   
[2026-10-26 13:38:29] mail         #9 OK   
[2026-10-26 13:38:29] mail         #10 OK   
[2026-10-26 13:38:30] mail         #11 FAIL mail() returned false
[2026-10-26 13:38:30] mail         #12 FAIL mail() returned false
[2026-10-26 13:38:30] mail         #13 FAIL mail() returned false
[2026-10-26 13:38:30] mail         #14 FAIL mail() returned false
[2026-10-26 13:38:30] mail         #15 FAIL mail() returned false
[2026-10-26 13:38:30] mail         !!! LIMIT REACHED: 5 consecutive failures, accepted total = 10
[2026-10-26 13:39:16] mb_send_mail #1 FAIL mb_send_mail() returned false
[2026-10-26 13:39:16] mb_send_mail #2 FAIL mb_send_mail() returned false
[2026-10-26 13:39:16] mb_send_mail #3 FAIL mb_send_mail() returned false
[2026-10-26 13:39:16] mb_send_mail #4 FAIL mb_send_mail() returned false
[2026-10-26 13:39:17] mb_send_mail #5 FAIL mb_send_mail() returned false
[2026-10-26 13:39:17] mb_send_mail !!! LIMIT REACHED: 5 consecutive failures, accepted total = 0
[2026-10-26 13:39:26] imap_mail    #1 OK   
[2026-10-26 13:39:27] imap_mail    #2 OK   
[2026-10-26 13:39:27] imap_mail    #3 OK   
[2026-10-26 13:39:28] imap_mail    #4 OK   
[2026-10-26 13:39:28] imap_mail    #5 OK   
[2026-10-26 13:39:28] imap_mail    #6 OK   
[2026-10-26 13:39:28] imap_mail    #7 OK   
[2026-10-26 13:39:29] imap_mail    #8 OK   
[2026-10-26 13:39:30] imap_mail    #9 OK   
[2026-10-26 13:39:30] imap_mail    #10 OK   
[2026-10-26 13:39:31] imap_mail    #11 OK   
[2026-10-26 13:39:31] imap_mail    #12 OK   
[2026-10-26 13:39:31] imap_mail    #13 OK   
[2026-10-26 13:39:31] imap_mail    #14 OK   
[2026-10-26 13:39:32] imap_mail    #15 OK   
[2026-10-26 13:39:32] imap_mail    #16 OK   
[2026-10-26 13:39:32] imap_mail    #17 OK   
[2026-10-26 13:39:32] imap_mail    #18 OK   
[2026-10-26 13:39:33] imap_mail    #19 OK   
[2026-10-26 13:39:33] imap_mail    #20 OK   
[2026-10-26 13:39:33] imap_mail    #21 OK   
[2026-10-26 13:39:33] imap_mail    #22 OK   
[2026-10-26 13:39:33] imap_mail    #23 OK   
[2026-10-26 13:39:34] imap_mail    #24 OK   
[2026-10-26 13:39:34] imap_mail    #25 OK   

How to read the limit

• mail() fails after N mails (returns false / exit code != 0): N is the accepted-per-window limit. If it starts working again after an hour, the window is hourly.
• mail() keeps saying OK but mails stop arriving at GMX after N: Strato silently drops/queues them - N is the real delivery limit. This is the sneaky one, only the inbox count reveals it.
• Run a big batch (e.g. count=100, repeat=10) via mail(), wait 10-30 min, then search GMX for LIMTEST-faad12.
• If mx_direct works, Strato's limit never applies - mails go straight from the webspace to GMX's mail server.
• If the probe shows "MAIL FROM ok without auth" for smtp.strato.de:25, the relay method also works without any login.