What email apps do you use on OSX and iOS to handle Gmail?

I use both Gmail and non-Gmail email, but I have a few Gmail accounts (work, school, personal), a Yahoo account I have to use for a website I work on, and a personal me.com account. I am looking for apps on OSX and iOS that support all of these. The native apps regularly have have problems with the outgoing Gmail servers and/or Gmail password issues. Apps like Airmail and Mailbox don't support Yahoo, and Mailbox is more of a triage app than an actual email app. I want a unified inbox, so the Gmail and Yahoo apps are out. At this point, my university email account can be added and can receive mail in it, but I can't send a damn thing with it set up as a Gmail account or through Exchange because it keeps on rejecting the outgoing mail server. Any suggestions?