Yellow flags/ weirdness

I’m less than 6 months into 1 day/week private practice, and had a client reach out to me for scheduling. I’m going to paraphrase our email exchange that happened after scheduling:

Client: can I pay you with a check?

Me: no, I accept cash, cards, Venmo, and cash app.

C: ok, I’ll pay you directly from my bank.

Me: unfortunately I can only accept the payment methods I listed before. If none of those work for you I will need to cancel your appointment.

That last email from me got bounced back twice after trying to send it. This is the auto reply: “your message couldn’t be delivered to (client email). Their inbox is full, or it’s getting too much mail right now.

What does that mean?? I’ve never heard of an inbox being full?! They filled out their intake form and their answers are vague but no red flags. So I don’t have any reason to cancel them necessarily. Their first name could be an indicator of a language barrier, not sure. But ignoring my payment methods is a red flag. The appointment isn’t for a few weeks so there is ample time to get cash from the bank. And the email getting bounced back is weird as hell.

When scheduling I offered them 11am and they asked to push to 10:30. I agreed, but then the other weird stuff happened and now I’m upset that my boundaries keep getting pushed with this person.

Here’s my plan, and I welcome any alternate advice. 1) Keep trying to email them to confirm my payment methods. 2) I am usually alone in the building on the day they’ll be there. I’ll invite my Very Strong Friend to be at the studio during their appointment to use the gym equipment and keep eyes and ears out.

Anything else I should be thinking about?