Azure mail (Linux VM) DNS resolving

Question

I install a brand new VM in Azure (debian). The thing is that the email i send isnt accepted by the remote mailservers. In my gmail the mail is received in my spambox and at my own webhoster the mail isnt even visible at all.

Ofcourse this can have several reasons and has todo with spam recognizion etc. The thing is that i see some errors in my mail headers what, i think, is causing the problems.

Received-SPF: temperror (google.com: error in processing during lookup of root@hstop40-w01.hstop40-web.a4.internal.cloudapp.net: DNS timeout) client-ip=137.117.203.77;

I have a cloud instance called hstop40-web and my server is called hstop40-w01.

I am kinda lost on what todo next. Hope that someone can help me fix this

Thnx

Answer 1

You need to ensure, at the most basic level, that reverse name resolution works for your SMTP host (i.e. 137.117.203.77 must resolve to the Fully Qualified Domain Name (FQDN) you use in your SMTP headers). If this isn't true you'll most likely get mail rejected from most public SMTP hosts (gmail included).

Beyond this challenge (which you can control by setting up DNS correctly) you might still get rejected mail because a lot of blacklists will inlcude IP address ranges from Azure and AWS (this is why both offer mail services - SendGrid on Azure and Simple Email Service (SES) on AWS).