Hi @JuliaFlanders,
OJS sends emails very consistently to the service it’s configured with (SMTP or local MTA, depending on your config.inc.php). From there, unfortunately, there are some subjective parts of the delivery process, mostly relating to email headers and addressing, and full-text (spam detection). This might result in messages getting spam-trapped at the receiver’s end, or not being delivered at all. OJS itself has no way of knowing whether this has happened after it has finished delivering to its configured delivery service.
To diagnose the problem definitively in a case where the recipient doesn’t have the message in their spam filter you’ll need to get access to the log files for the service OJS uses to deliver mail. You may or may not have access to this depending on your service provider’s specifics.
The likeliest cause is a DMARC violation; there are a few threads in this forum about DMARC compliance that might help.
Regards,
Alec Smecher
Public Knowledge Project Team