When a user completes a paid membership via paypal, the thenk you reciept email from civicrm is bounced back by gmail. This is a brand new problem we are seeing -- never has been a problem in the past. Any help apppreciated.
From the bounceback:
Diagnostic-Code: 550-5.7.1 Gmail has detected that this message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked.
There multiple of reasons that gmail might reject your mail. In general, gmail has been getting more and more stringent with the usual indicators of 'unsolicited mail', and given that the content probably hasn't changed, it's most likely due to DKIM, SPF or DMARC headers.
If you can look at the original sent message from you server (e.g. trigger one to your own gmail address), then you can see those three headers and identify which one needs to be addressed.
Another thing to consider is the "from" address that you're using (configured in the contribution page) - if you recently changed that, e.g. to a gmail address, then that is likely the source of the issue. You won't be able to reliably deliver mail that is "from" a gmail address if it's coming from your civicrm install.
