Even though Postmark is up and not reporting any issues on the status site, you may encounter cases where your application cannot connect to Postmark. The most common causes for these issues are related to networking configuration changes that might have occurred in your environment, or done by your hosting provider without your knowledge.
What we need to confirm is:
- You server(s) can lookup the IP address to connect to our API or SMTP servers.
- You are able to connect to our servers from your server(s). Ports 80 or 443 for the API, and ports 25, 587, or 2525 for SMTP.
When contacting us, please provide us with the public IP(s) that your server(s) are connecting from, we will be better able to look at logs for connectivity issues on our end.
Below are the commands we ask you to run from your server(s), if you can provide the full output from these commands when contacting support, we will be much better able to assist you in sorting out connectivity issues:
Troubleshooting API Connectivity:
First, verify that DNS is working properly:
$ nslookup api.postmarkapp.com
$ curl -vvv https://api.postmarkapp.com
$ curl -vvv -k https://api.postmarkapp.com
$ curl -vvv http://api.postmarkapp.com
$ time curl -vvv https://api.postmarkapp.com
Troubleshooting SMTP Connectivity:
$ nslookup smtp.postmarkapp.com
$ telnet smtp.postmarkapp.com <port> EHLO localhost QUIT
telnet smtp.postmarkapp.com 25 Trying 18.104.22.168... Connected to smtp.postmarkapp.com. Escape character is '^]'. 220 smtp.postmarkapp.com ESMTP p-pm-smtp02-pktewr1 EHLO localhost 250-smtp.postmarkapp.com 250-PIPELINING 250-SIZE 20480000 250-VRFY 250-ETRN 250-STARTTLS 250-AUTH PLAIN LOGIN CRAM-MD5 DIGEST-MD5 250-AUTH=PLAIN LOGIN CRAM-MD5 DIGEST-MD5 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN QUIT 221 2.0.0 Bye Connection closed by foreign host.<br>
$ swaks --auth --tls -s smtp.postmarkapp.com --to="email@example.com" --from="firstname.lastname@example.org" --port=25<br>