Sporadic SMTP Mailer Errors

ColorFlakes

This morning about 5 hours ago I started to receive Mailer Errors in the System Logs. There are always two errors included with each failed email.

Unable to email via Sendmail Unable to send mail: mail(): Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set()

Is always followed by
Unable to email via SMTP: service@company.com (tls://smtp.outlook.com:587/SMTP) 4.7.0 Temporary server error. Please try again later. CPRX1 [CH2PR03CA0007.namprd03.prod.outlook.com 2024-11-25T17:46:17.585Z 08DD0D7238AE75CC]

This happens to roughly one out of every three emails going out. I've sent some diagnostic emails from the Admin Panel and sometimes it's successful while other times it is not. When it fails at adds another two failure entries to the System Logs.

I've checked both the PHP and IIS logs and don't see any errors. Any suggestions?

KevinTheJedi

ColorFlakes

The error returned directly from Microsoft states: 4.7.0 Temporary server error. Please try again later. It doesn't specify what that error is so I'd recommend reaching out to their support to see what's going on. The second error of "Unable to email via Sendmail" simply means SMTP failed so it tried using local Sendmail to send out the mail as a last resort but that failed as well (likely not configured properly).

One thing I did notice is you are using smtp.outlook.com for the SMTP hostname when it should be smtp.office365.com. Maybe update the SMTP hostname and retest to see if it improves?

Cheers.