Error sending emails with phpMail and SMTP

[krokos]

Hello, 

since yesterday the automated Welcome messages are not delivered. I noticed when I received a message that the welcome message was not delivered since it was marked as spam.

1. I logged in the admin area and tried to send it manually again. I got an error "Could not instantiate mail function" since phpMail was enabled. 
2. I then switched to SMTP and I received another error "Data not accepted"
3. I checked the Activity logs and I see these errors:

Email Sending Failed - SMTP Error: data not accepted. (Subject: Digimouse - New Account Information)

WHMCS version: 7.5
PHP version: 7.2

[Vox]

Hi Krokos,

It may be an outbound SPAM filter issue. I had an issue like that previously.

Please check the links in the thread below.