Not receiving emails on my iMac or Phone or iPad

Mail Version 16.0 (3826.700.81). iMac 15.6.1 (24G90). Webmate handles my mail. I have been onto the webmate site and purposely put various email addresses from senders whose emails are not being received on my 'White List' and also noted that they are not spam. Nevertheless my wife has an Android phone and a different email address and she receives these emails without any problem. If she forwards them to me I do not receive them. I have had this issue for the last three years (have purchased new iMac during this time) and webmate do not have an answer despite several attemptsexcept suggesting this is an Apple or software / hardware fault. I'm in the middle of selling / buying property and am not receiving any email from our solicitor who is handling the conveyancing. Have checked all 'White List'. and Spam settings, always look in my spam folder, but no sign. Am caught between Email histing and Apple with, it seems, an insurmountable problem. Would like to fix but no idea. Have used Apple professionally for 25 years or more.