Thank you for your very speedy reply – much appreciated! Glad to learn that it’s not a WordPress update issue and that your plugin works with 5.3.2 Clearly the problem lies elsewhere.
Incidentally, I made a typo in the website address…it’s https://imaginelot450.ca
Our club website (www.malanat.ca) experienced identical symptoms.
With no immediate acknowledgement being provided to the sender apart from a “small spinning wheel”, multiple emails kept arriving, with much frustration all around.
In our case the problem was apparently caused by Contact Form 7 Honeypot
https://en-ca.ww.wp.xz.cn/plugins/contact-form-7-honeypot/
Once uninstalled, everything appears to work as it should.
A previous comment mentioned using Flamingo as a useful second method of testing and archiving email submissions – I heartily agree – but I think the key point here is that it’s likely a plugin that’s causing the behaviour.
