I know someone who is a consummate professional BUT I have chided him about his AOL email account in fun. He now has a gmail account as well BUT prefers his AOL account. I think one reason is that he probably gets that, "You got mail" vocal notification. He never has explained to me why he has held on to it for so long BUT he is in the medical field so it works for him. The patients that really need him don't care as long as they can get in touch with him. He was hacked and I immediately explained to him what to do. He decided to close one AOL account & open another. That was not my recommendation. LOL
I am not a geek, I have friends who are BUT I have dual booted my computers Windows/Linux and also from time to time use a Linux OS that I loaded on a flash drive that doesn't require a hard-drive to run without their help. Puppy Linux is really genius. I have used it for 7-8 yrs. I use Zorin for my every day personal and business computing. I am using it now. I just update Win10 every month and use it only when I have to.
I've used Microsoft products since DOS 3.X and my fave OS is Win2K by them but Win7 for me was pretty cool. Hated Win8, ain't crazy about Win10 but it is not as bad as a tooth extraction, without anesthesia, which Win8 was. Loved Paradox as a language and relational database product that you DID NOT have to program unless U wanted to. Borland really had better products than Microsoft at the time ... those were the days.
But I digress, why, because although I set up my own website, it's OK not great BUT functional, and I pay Google for my "professional look" email, I love using my flip phone, especially pulling it out at family functions and seeing my nephews & nieces cringe with embarrassment because they are all "smart phone" users. BTW, I did purchase my first tablet last yr. An Android, of course. LOL.
A long way to no regarding their email preferences but I admit that I have some tech prejudice even when business folks may use a free gmail account in business activities. However, I have had partners that used a custom email address, great websites and ended up being the worst to do business with. Especially, many times if they were VC backed.
Consequently, just do your normal vetting and go from there.