The problem was the two-step verification process with iCloud. Basically, if you want to use Thunderbird and iCloud together you have to generate an app specific password when you log into the Apple ID website. Here's a link that has the instructions.

If you are signed in to iCloud for Windows, you don't need an app-specific password when using your Apple ID with third-party Microsoft apps. To generate and use app-specific passwords, your Apple ID must be protected with two-factor authentication. Sign in to iCloud to access your photos, videos, documents, notes, contacts, and more. Use your Apple ID or create a new account to start using Apple services. When open Mail > Preferences > Accounts and select iCloud, select Server Settings and click on the blue button to the right of the account name, there are 2 accounts named iCloud. If I select the first account, then click the blue button again and select Edit SMTP Server List…, the Advanced button displays a long number for TLS Certificate. Enter your iCloud password, which is case-sensitive, in the password field Next, set up your SMTP settings for outgoing mail: Enter the SMTP Sever Name: smtp.mail.me.com

The above iCloud SMTP is not listed in the SMTP servers list Connection Doctor doesn't check the outgoing iCloud setting either - just as if it didn't exist. According to Apple's KnowledgeBase on iCloud Email the SMTP server is smtp.mail.me.com, but Mail.app reports an invalid SSL certificate

SMTP Settings Hostname: smtp.mail.me.com Port: 587 Encryption: STARTTLS User name: Your user name - the first part of your email address, without @me.com. Published: 18 April 2019. All product names, logos, and brands are property of their respective owners. All company, product and service names used in this website are for identification

iCloud account; Exchange 2010 account; Exchange 2013 (Office 365) account; IMAP account; Interestingly only two accounts show up in the "Outgoing Mail Server (SMTP)" drop-down list. The outgoing server related to the IMAP account always shows, plus the outgoing server of the selected account.

Sometimes I forget that there are people who use and/or want to use iCloud on a device other than one made by Apple or via a 3rd party email app. On many occasions, those email apps need to be manually configured with information other than an email address and its associated password. Well, below is the SMTP (outgoing) server information needed to be able to SEND iCloud email via a 3rd party trying to setup icloud email in outlook but get multiple errors. use imap port 993 and smtp port 857. can't connect to imap server or smtp server. Outlook wont open until I setup a profile. smtp.mail.me.com:25:0 --> worked and still works! No clue why this port does the trick on my machine, but those with this problem, best is to try the above variations and see what works for you and report it her. Office 365 is a cloud platform that businesses use for their day-to-day activities and make their environment more collaborative. The email server of Office 365, namely Exchange Online, is popular among enterprises. Office 365 end users configure their accounts on Outlook to access their mailboxes. The process is similar to web mail users configuring their When you use this port, the outgoing mail goes through the ISP's SMTP server. To work around the problem, many third-party hosts offer access to their SMTP server via a port other than the standard port 25. For example, the iCloud SMTP server (smtp.icloud.com) also accepts connections on ports 465 and 587. It's pretty easy. It requires a bit more input, but work perfectly. Follow the same step as when you add new Gmail account. You'll be prompted to choose which emails provider you want to choose. You'll see Gmail (obviously), Outlook, Yahoo, etc. A