I wrote this on September 7, 2021 and published it on linkedin. However I found that it can be hard to search if I put there. so I put here anoter copy TLDR: if your external SMTP is using port 80 instead of standard ports in an istio mesh, create a Service Entry for the external SMTP. These two days, a strange timeout issue happened in one of our kubernetes clusters when trying to send emails via SMTP even though the same configuration works perfectly on our development machines.

TLDR: if your external SMTP is using port 80 instead of standard ports in an istio mesh, create a Service Entry for the external SMTP. These two days, a strange timeout issue happened in one of our kubernetes clusters when trying to send emails via SMTP even though the same configuration works perfectly on our development machines. At first, I thought it was due to SecureSocketOptions.startTLS. I changed it to SecureSocketOptions.

Two days ago, our web applications need to get clients' real IP address. Our sites is hosted in kubernetes, isito is used for ingress controll. behind cloud load balancers, it is not easy to make it work. There are two ways to do that in alibaba classic load balancer: http/https listeners, and TCP listeners with proxy protocol HTTPS listeners is crossed out due to certificate issue. HTTPS listeners can use integrated certificates or self uploaded certificates.