[cb500]

I just tried it in another email provider's web interface. Set up a trial account. Imported the Fastmail CSV file. Their pulldown menus worked fine when starting to type an address. Within Gmail I experience the same issue in both Chrome and Firefox (latest 64-bit version of each browser running in Windows-10 on a desktop). It seems to narrow down to an issue only in Gmail. If this was a general issue with Gmail I'd think a web search would turn something up. So it must be something I have done, or am doing. I just tried a Chrome Incognito window and the problem is still there. Firefox I have default to Private Browsing, so the cache, cookies, and other files are not saved.

One other interesting aspect. When I delete all Google contacts and re-import the same CSV file, the results are different. A different set of incomplete addresses shows up in the pull down menu when I start to type an address. I just received four (4) addresses in the pull-down list upon typing "C" in the To line of the compose screen. I got rid of the draft, deleted the entire contacts, re-imported the CSV file, went to a compose screen and typed "C" in the To line, and this time got six (6) addresses, some different than the last time.

I use the Auto bcc extension for Chrome, so as to not have to manually enter a bcc. However, I've been using that for over a year. And, in Firefox such a browser extension is not running yet the same behavior happens in the Gmail compose screen. One feature I like about Fastmail is Auto bcc.