There, I’ve said it. Hopefully anyone else Googling for this will find it now!
I spent a better part of yesterday checking all my firewalls because I couldn’t connect to port 25 of public mail servers from my VM. As a SysAdmin I have an Exchange VM etc. in my home lab that I wanted to setup for outgoing email … and when I couldn’t connect to port 25 I wondered whether there was something wrong with my network configuration or firewalls (being a VM there are layers of networking and firewalls involved). Turns out none of these is the case. My host itself cannot connect to port 25. The ISP is blocking it – simple!
This is Etisalat at home. Things might be different for business connections of course. And, this is nothing against Etisalat – many ISPs apparently do this to block spam, so this is standard practice. First time I noticed that’s all.