We just made the switch to Verizon.
Setting up Mail.app with my relatively new MacBook Pro (and OS 10.8.4) was very smooth.
Not so with my wife's old PowerBook G4 running 10.5.8, which she inherited from my daughter.
It seems to set up fine, using the same settings for the servers as on the MBP (it has to be done manually), but it is unable to send mail (via the verizon smtp server). The Connection Doctor thing does not have any trouble finding the servers and connecting.
I get the "The sender address firstname.lastname@example.org was rejected by the server smtp.verizon.net." message.
These settings work when sending email from this verizon account from her iphone, or from my MBP.
I successfully set up my .me email account on the G4 and that was able to send mail.
Couldn't find anything online to shed light on this. Any help would be appreciated. Thanks
Your asking peers here.
You didn't say which settings you were trying to use. Lots of people are posting about switching over to the latest EMAIL settings which include pop.verizon.net and smtp.verizon.net as the servers. However it has invariably been a mistake they are making or a special requirement of there DEVICE such as a shutdown and restart.
You should take a look at http://verizon.com/emailsettings . There are both the manual settings and some automatic trouble shooters that may be able to setup your device.