Tried to set up Mail on a Mojave install. I turned on logging in the Mail Connection Doctor and found this:
INITIATING CONNECTION Sep 27 15:34:24.920 host:imap.gmail.com -- port:0 -- socket:0x0 -- thread:0x600000a7f780
Shouldn't this be port:993??
null-OTHER, macOS Mojave (10.14), Mail
The SMTP portion works fine as it is connecting to the appropriate port:
INITIATING CONNECTION Sep 27 15:34:54.970 host:smtp.gmail.com -- port:587 -- socket:0x0 -- thread:0x600000c010c0
CONNECTED Sep 27 15:34:55.030 [kCFStreamSocketSecurityLevelNone] -- host:smtp.gmail.com -- port:587 -- socket:0x600003c29380 -- thread:0x600000c010c0
Gmail - could not connect to this IMAP Server
