Canot reply to PM

When I try to reply to a PM from a interested party following a ‘for sale’ listing I get this from Gmail:

## Delivery incomplete
There was a temporary problem while delivering your message to Gmail will retry for 45 more hours. You’ll be notified if the delivery fails permanently.

This has happened before and eventually I get a ‘cannot deliver’ message. Am I doing something wrong? Annoying as the enquiry was from someone who wanted to buy an item!



The receiving service is blocking the messages (perhaps a bad spam classification for the servers). There is nothing you can do to fix this. If the intended recipient of the PM logs on to the forum they should see the green message notification.

Thank you, it’s frustrating!