I currently have an email address, [email protected], that I currently use to forward to a gmail account that I've used for years. I currently have it set, so I can send email from my [email protected] instead of [email protected].
This is done through the web ui on my current domain name, provider, gandi.net.
What are the main differences between this arrangement, and setting up a Google Apps for your domain setup, where I'm explicitly listing in the dns records to point records to point to Google's app mail server?
When you forward mail to Gmail, your IP address is the source for all the mail, spam and otherwise; if you start mostly forwarding spam, then your spamminess score will go up and you'll find it harder to email other Gmail users.
See http://research.google.com/pubs/papers_by_year.html and "Sender Reputation in a Large Webmail Service".
When the mail is received directly by Gmail, it can use the source IP as a reasonable filter and you won't be harmed.
Well, some services refuse to accept mail when the mxserver and the domain are different (sixxs for example). With using your own domain, and google, gmail acts as a mail client- while you have the gmail interface, your access is as reliable as your own server, and you adminster accounts yourself. With google apps, you use gmail as a server (so your mxrecord is for gmail), run the gmail client.
'easier to manage' is relative to what your current setup is. google apps has a nice neat web based way of running accounts, identical to the normal client, pretty much. You also have a bigger mailbox than many shared hosting accounts.
Spamwise, google has a great system. Whether it'll be better than a spam filter you set up yourself... is relative. They have more input, of course, but a good baysian filter will ,likely,eventually be just as good
The technical difference is obvious: different servers accept the mail.
There are any number of implications, and the value is purely subjective.
Which one does a better job of efficiently rejecting spam? Which one has better uptime for accepting emails? Which one has more geographically dispersed secondary mail machines to accept traffic when the main machine is down? Which one is easier to manage, for instance setting up alias addresses or filters. What do you pay currently (Google Apps basic is free, ad driven).