I can't add my Outlook account to my Gmail app on iOS

Hello Daniel Remian,

Thanks for your post and let us know above information. 

Firstly, as you mentioned your account has 2FA enabled, please make sure you are using the APP password when trying to add your account to the Gmail APP on iOS. As you mentioned you are using a Microsoft 365 Business Basic plan, you can refer to this article to create the APP password: Manage app passwords for two-step verification.

Moreover, since the Gmail account also support 2FA, it is recommended that you can try to sign to the Gmail for iOS APP with the Gmail account (which has 2FA enabled) and check the result.

Additionally, we would like to suggest that you may also try to download the latest version of Outlook for iOS APP on your device and check if you are add your outlook account to the Outlook for iOS APP.

Hope above suggestions can provide some useful information to you. If you prefer to use Gmail for iOS APP and need further assistance to add the Outlook account to it, as our team is focusing on Microsoft 365 products and services, you are recommended to contact Gmail support team to get further target assistance. 

Thanks for your understanding and cooperation.

Best regards,

Jennifer

Hello Jennifer,

Thanks for your reply. 
However, after I posted the question I had found out how to turn off 2FA, but it didn't help. I also created an app password like you said and tried logging in with it, but I'm getting the same "Your username or password is incorrect" message. 
As far as Outlook and Gmail apps I can confirm both things you asked about:

- I can add my 2FA enabled Google account to my Gmail iOS app
- I can add my Outlook account to the Outlook iOS app both with and without 2FA enabled, but for some reason I can't add it to my Gmail app... 

Also, I found a weird problem - sometimes when I try to log into my office365 account on pages like live.com and other, I get this message: "That Microsoft account doesn't exist. Enter a different account or get a new one.". That is obviously not true as I am able to log into my onedrive and outlook desktop with the same credentials. Could that be somehow related to my gmail problem?

Ok hi Jennifer,
unfortunately I still haven't heard from google regarding my problem so I've tried other e-mail clients and it's it's just as I expected. It's not just gmail that I can't log into. It's every single e-mail client except Outlook. I've run out of ideas and am running out of patience... I must have changed some settings because it can't be this hard to add an outlook account to other email clients. After extensive research I think it has something to do with the fact that I'm using my custom email (with my own domain) as my login, which I've added while setting up the Office Business Basic account. Please help, I need to finally resolve this issue.

(Edit: after extensive research and a long phonecall with a fantastic Microsoft's technician named Andrew - I've found that there's a problem with work or school Outlook and Exchange emails when logging into Gmail. It's been like that for a year or so. I will raise this issue with Google and hope for a resolution. Until then, though, I will switch to the Outlook app.)

Hi Daniel Remian,

Greetings. About your problem with the Gmail for iOS APP, we recommend you may try below methods to see if it helps:

1. Make sure to update your Gmail APP to the latest version and make sure the Gmail for iOS APP support OAUTH 2.0 so it can access your exchange online mailbox (you may need to contact the Gmail support again to confirm this information).

For your reference: Announcing OAuth 2.0 support for IMAP, SMTP client protocols in Exchange Online. 

2. Clear the password caches on your Gmail for iOS APP.

3. Try to manually setup your account in Gmail for iOS APP. For detailed information about the IMAP and SMTP settings for Microsoft 365 account, you may refer to this article: POP and IMAP email settings for Outlook 

Regards,

Jennifer