Some, not all of the mails that are forwarded from my alias to my gmail account don't reach me. i.e recently mails from a conveyancer go missing maybe 1/2 the time. No error messages are reported and they are not in spam that I can find.

In an effort to work around I set up a distribution list and tried to use both my outlook and my gmail address. The verification messages don't make it to gmail although they do to outlook. If I then forward that message from outlook to gmail it goes through most of the time. I am sure it is being dropped for some reason by gmail but I get no indication of why that is.