Gmail not receiving emails

[HerestoyouMrsRobinson]

Some emails are not reaching my gmail account - hotmail and aol, other stuff is getting through, any ideas why?

GMail has fairly aggressive spam filtering. Check that the missing emails aren't in your trash folder. Also check with the sender to see if they are receiving bounce messages. If they are getting bounces it is likely that their email server does not meet Google's requirements. Any professional email service should be ok but some people set up their own email servers and don't realise there are some special steps if they want GMail to accept their emails. This is a particular problem if they are running a mailing list as GMail is likely to decide they are sending spam.

Not in spam and not getting bounce messages.
Emails that are replies to one that originates from the gmail address get through...