Unable to send e-mail: 454 TLS not available due to temporary reason

Every time I sent an e-mail via the Messaging API I get the following error. This is preventing my live app from sending e-mails to customers. I originally sent a private message but here is the public message you requested.

{“code”:5053,“message”:“Cannot send email. Error: 454 TLS not available due to temporary reason\n”}

I’ve tried multiple apps, two different accounts and two different mail servers with multiple accounts and it’s all the same error. I’ve tried it with both Java and REST APIs, same error.


Hi Simon,

What settings and email provider do you use?

Up until a few days ago it worked with port 25 + TLS. I’ve tried other options (port 25/465/587) with both TLS and SSL but all yield the same error.

Can you please provide your application ID?

I just sent it to support@backendless.com

Are you sure that the problem is not with your SMTP server? Can you somehow try to send an email directly from the your mail server?

I’m able to send a mail directly from my mail client.

Is there anything in the logs that indicate what my error may be? By the way, I tried saving the SMTP settings and get the error “Username and password not accepted.”. Does the “Test” option have to pass before I can “Save” settings?

There’s nothing in the logs except the message you see, unfortunately. And yes, the Test should pass before saving the settings.

Can you also check whether the settings are the same when you send a message directly from your mail client?

I just re-saved the mail settings using 465 + SSL, both Test and Save were successful but I still get the error when trying to send an e-mail through the API.

Since the Test passed, maybe the error is related to the recepient? Have you tried to send email to another email address? Also you may try to click Test some more times in order to make sure that it passes consistently.

Ok, now a mail went through.

I believe this could be some temporary problem with the mail server you use, since I checked Gmail, for example, and it worked fine. If you’re using some provider’s mail service, I would also suggest contacting their support to get any additional information.