Failed to send email using Postmark

[kkostov]

I'm having trouble configuring remark to use Postmark's SMTP. The operation fails with a tls related error:

2022/05/15 08:36:22.369 [INFO]  {rest/httperrors.go:39 rest.SendErrorJSON} failed to send confirmation - failed to make smtp client: failed to dial smtp tls to smtp.postmarkapp.com:587: tls: first record does not look like a TLS handshake - 500 - xxx.xxx.xxx.xx - xxx [caused by auth/provider/verify.go:188 provider.VerifyHandler.sendConfirmation]

My SMTP settings are as follows:

SMTP_HOST=smtp.postmarkapp.com
SMTP_PORT=587
SMTP_TLS=true
SMTP_USERNAME=***
SMTP_PASSWORD=***

I did find a few other issues discussing TLS but I couldn't find a way to make it work.

Postmark offers two main ways to authenticate, the one that seems compatible with remark is "SMTP Token".

I tried using any of the supported ports - 25, 2525 and 587 as well was setting both SMTP_TLS=true and/or SMTP_STARTTLS=true.

Is it possible that I'm overlooking something?

Thanks

[paskal]

Port 587 is used with StartTLS, 465 is the standard TLS port. Please try using 465.

[kkostov]

I did try that as well (it was a recommendation in other issues), however port 465 doesn't seem to be in use by Postmark.

Don’t use port 465 for SMTP if you don’t have to. Many modern hosting providers and email service providers block it or don’t support it (including Postmark).

Calls using 465 result in a timeout (as if there is no service listening there).

The guideline from the postmark docs appears to be to use 587:

Port 587 was established as a modern secure SMTP port for message delivery. It supports TLS natively and STARTTLS as well, allowing for the secure submission of mail over SMTP.

[umputun]

well, apparently this "supports TLS natively and STARTTLS as well" doesn't work with go-pkgz/email library which is a thin wrapper on top of go stdlib. If you can reproduce the issue with some small snippet you can submit a ticket to that library.

Another thing - what version of remark do you use? Support of STARTTLS is not in latest, but in master only.

moved to discussions