Solved 3CX SMTP Not Delivering Emails to One Domain — Please Check Bounce List

[GML]

Hi,
We are experiencing an issue where voicemail‑to‑email messages and test emails fail to deliver when using the 3CX SMTP service, but only when sending to a specific external domain.

PBX Type: Hosted by 3CX
SMTP Mode: 3CX SMTP
Problem: Emails to one of our customers domains are not received
Scope: Only this destination domain fails

Symptoms:
3CX reports emails as successfully sent
No error logs
Voicemail emails simply never arrive

What we tested:
Switching to an external SMTP provider
- Emails deliver immediately
Sending to other domains while using 3CX SMTP
- Works as expected
Switching back to 3CX SMTP
- Emails to our customers domain stop again

Because the PBX works normally with another SMTP server, but messages disappear when routed through the 3CX SMTP and only for one domain, this seems consistent with 3CX’s SMTP bounce‑list behaviour, as described in previous cases where a domain had to be manually removed from the bounce list by 3CX staff.

Could someone from the 3CX team please check whether our customers domain has been added to the 3CX SMTP bounce list, and remove it if so?

This is affecting voicemail notifications for our customer, and everything points to the domain being blocked upstream at the SMTP layer.

Happy to give the domain in a dm

Thanks,
Brad

 

[Alphabetic]

Obvious one, but have you checked the anti-spam filtering on this particular domain and also check your domain to see if its on any blacklisting?

 

[DimitrisL_3CX]

Hello @GML,

Please be advised to open a ticket in our Customer Support department via the Contact Form so we can check this further.
Keep in mind that we are not able to check the domain only, you will have to share the full email addresses that you are experiencing this.

 

[GML]

Hello @GML,

Please be advised to open a ticket in our Customer Support department via the Contact Form so we can check this further.
Keep in mind that we are not able to check the domain only, you will have to share the full email addresses that you are experiencing this.

Thanks Dimitris, ticket created

 

[GML]

Thanks both, turns out we were on the bounce list but all working again now we've been removed

 

[DimitrisL_3CX]

Thank you for the update, and glad that this is resolved now.