My mailserver is very German. When your mailserver tries to send a message, it does a reverse lookup on the IP address. If that doesn't deliver a valid hostname, you're out. But we are not done yet. If it gets a valid hostname, it does an A (IPv4) or AAAA (IPv6&) lookup on that hostname. And if it doesn't deliver back the same IP address, you are still out. It is fascinating to observe how often that uncovers that even big names get their DNS wrong. Hello, Spamcop ;)

#ItsAlwaysDNS #MailAdmin

My mailserver is very German. When your mailserver tries to send a message, it does a reverse lookup on the IP address. If that doesn't deliver a valid hostname, you're out. But we are not done yet. If it gets a valid hostname, it does an A (IPv4) or AAAA (IPv6&) lookup on that hostname. And if it doesn't deliver back the same IP address, you are still out. It is fascinating to observe how often that uncovers that even big names get their DNS wrong. Hello, Spamcop ;)

#ItsAlwaysDNS #MailAdmin

Noticeable trend on my mailserver: Spam that comes via IPv6 is 90% from Google servers and the rest is Amazon or Microsoft servers. So far no other senders of IPv6 spam. 95% of spam attempts are still IPv4 from various Chinese, US, pacific country sources. The most annoying spam sender stays hostgnome from UK. (All of these attempts are blocked by my mail server, so never make it past the initial HELO part).

#SelfHost #MailAdmin

Hostgnome uses a simple tactic. They rent/buy IPv4 address pools, send spam via all allocated addresses in that space for a few days and then get rid of the pool, replacing it with a fresh one. So it makes sense to have a cronjob that checks their ASes and immediately block all pools on the firewall.

#SelfHost #MailAdmin @homelab

Noticeable trend on my mailserver: Spam that comes via IPv6 is 90% from Google servers and the rest is Amazon or Microsoft servers. So far no other senders of IPv6 spam. 95% of spam attempts are still IPv4 from various Chinese, US, pacific country sources. The most annoying spam sender stays hostgnome from UK. (All of these attempts are blocked by my mail server, so never make it past the initial HELO part).

#SelfHost #MailAdmin

A noticeable uptick in phishing mail coming from Google's mail servers. Trying to report them has turned out to be fruitless. If anyone know where to best send reports so that the Google geniuses take a look and action, please do tell me!

#SelfHost #MailAdmin

A noticeable uptick in phishing mail coming from Google's mail servers. Trying to report them has turned out to be fruitless. If anyone know where to best send reports so that the Google geniuses take a look and action, please do tell me!

#SelfHost #MailAdmin