it depends if the receiver has an autocrypt-capable email client like k9mail, etc. it doesn't have anything to do with IMAP on the receiving end, but Delta Chat

it depends if the receiver has an autocrypt-capable email client like k9mail, etc. it doesn't have anything to do with IMAP on the receiving end, but Delta Chat currently only supports IMAP so the sender does need a server with IMAP support to use Delta Chat, but the receivers don't even need to have Delta Chat