Email content not loading on iPhone or iPad via Wi-Fi since iOS 15

After a year trying to resolve this issue of email content taking ages to load on the Mail app on iPhone and iPad via Wi-Fi since iOS 15, and eventually giving up on it and using other email clients, I now seem to have accidentally resolved it by changing the DNS server. I did this because my broadband company had a national outage due to issues with their DNS servers, and the advice on Twitter/X was to change to one of the Google servers 8.8.8.8. It worked for my broadband and it also seems to have worked for Apple Mail. I can’t say I feel entirely comfortable with using a Google server, but it seems to be safe as far as I can find out. Anyway, I’m not techie, so I have no idea why it works for Mail as well as broadband, but it does seem to. Hope this helps some other folks. If anyone has a major red flags for Google servers, do let me know!