Do I have to, and how do I setup bounce emails HELO command?
Skippy le Grand Gourou asked: Our server has been listed several times on CBL (see this question) because it “attempted to send email without using the HELO/EHLO command”. Grep’ing on …
Postfix transport map always using catchall definition
user203913 asked: Hoping one of the Postfix experts on here can help me debug an issue I am having with transport maps. I’ve gone through a the recommend list of …
Which side of this SMTP conversation is correct?
Mike B asked: I have an odd scenario with two mail servers communicating with one another and need help determining which one is behaving correctly. It’s a little complicated to …
Detect spammers on my server
mfuesslin asked: I recently got one Undelivered Mail Returned to Sender while sending my newsletter to one of my 1500 customers. My website uses a double-opt-in procedure to make sure, …
How to configure Postfix to send specific error code for a domain?
Henno asked: I need to configure Postfix to send 451 4.7.0 Temporary problem, please try again later for a specific domain. I have tried to google for returning custom error …
What's the point of repeating an email address in "The Envelope" and the "The Header"?
TLDR asked: I learned that both the FROM address and the TO address is repeated in a hidden element called the “envelope”, and then repeated again in the “body”. Question …
Multiple mail servers and reverse DNS
leeeennyy asked: If I have three mail servers MS1, MS2 and MS3 all with different IPs but share the same domain name (exampledomain.com) and I use an SPF record to …
Bypass Postfix 'reject_unknown_client_hostname' for authenticated SMTP clients
tcdaly asked: In my postfix configuration, I’ve switched on smtpd_client_restrictions = reject_unknown_client_hostname as an anti-spam measure. However, sometimes I fall foul of this myself when I make an authenticated SMTP …
nginx/php-fpm – 405 Error Submitting Email Contact Form
4oo4 asked: I have a small Ubuntu 16.04 VPS that’s running nginx/php-fpm to run a WordPress site, and running an SMTP server through Postfix/Saslauthd. My mail server is working just …
Sending malicious email as a test
Orphans asked: I have set up a working SMTP relay together with MailScanner. This SMTP relay is not — and will not be — able to relay email from the …