SB, I too have AOL and cable, with AOL principally being used for email.
For folks like me, AOL has what they call "Bring Your Own Access (BYOA) Plan." This plan charges $14.95 per month, which includes unlimited AOL usage through an Internet connection not provided by AOL. It also includes five free hours of dial up access in the U.S. each month, and each hour is only $2.95 per hour after that.
I hate to ask, but does your client still have his AOL account or was it somehow cancelled when he switched ISPs? Is it that he is not receiving mail or just TIFFs? I am uncertain what the file size limit AOL has imposed, but if the TIFF file is very large, perhaps that has something to do with the problem.
And finally, as a check, you can send the file to me and then I’ll let you know what happens.
Harv