If you try to add a Google Workspace mailbox to a sequencer by uploading an SMTP username and password, the connection fails with an error like 535-5.7.8 Username and Password not accepted. This is expected, and it isn't a problem with your mailbox.
Why the password upload fails
Google does not allow plain password authentication for Workspace accounts. Sequencers therefore cannot connect a Google Workspace mailbox from an SMTP/IMAP credentials list the way they can with a standard SMTP mailbox.
How to connect a Google Workspace mailbox
Before adding mailboxes, ensure that your sequencer is configured in the Maildoso settings. In your sequencer, choose the Google / Gmail connection option rather than the generic SMTP or CSV upload option.
Sign in with the mailbox address when prompted, and authorise the sequencer.
You have full administrator access to your Google Workspace account. The mailbox password and the one-time code needed to complete sign-in are both available in your Maildoso dashboard — see Logging in to your Google Workspace mailboxes (password and one-time code).
Repeat for each mailbox, or use your sequencer's bulk Google connection flow if it offers one.
Alternatively, you can connect mailboxes directly from the Maildoso dashboard. Navigate to the Settings menu, go to the Sequencer section, and link your sequencer. Then, in the Email Accounts section, filter the list of mailboxes by selecting "Provider = Google," select the desired mailboxes, and click "Add to sequencer."
How to tell which mailboxes are connected: the sequencer logo
Once a Google Workspace mailbox has been added to a sequencer from the dashboard, its row on the Email Accounts page shows that sequencer's logo in the column next to Status (for example a small round PlusVibe, Instantly or Smartlead icon). That's the quickest way to check which Google Workspace mailboxes are already connected and to which tool. Two things to know:
The logo only appears for mailboxes connected with Add to sequencer. SMTP mailboxes are uploaded to a sequencer by CSV, so their rows stay blank in this column even when they're connected and sending — a blank column on an SMTP mailbox is not a sign it's disconnected.
A mailbox that shows the logo but isn't sending in the sequencer is usually a sequencer-side issue (paused, removed from the campaign, warmup disabled) rather than a Maildoso connection problem — check the mailbox in the sequencer first, then see Troubleshooting sequencer connection errors.
Connecting many mailboxes
Connecting dozens of Workspace mailboxes one by one is slow. You can connect multiple mailboxes directly from the Maildoso dashboard by filtering the Email Accounts section by "Provider = Google," selecting the desired mailboxes, and clicking "Add to sequencer." If this flow keeps failing part-way through, or your sequencer does not support bulk connections, contact us with the list of mailboxes and the sequencer you're using and we'll look at it with you.
What about SMTP mailboxes?
Standard Maildoso SMTP mailboxes are different — those connect with a username and password, and are uploaded to your sequencer as a credentials file (Email Accounts → select mailboxes → Export selected to CSV). The "Add to sequencer" button is for Google Workspace mailboxes only; for SMTP mailboxes use the CSV export. If an SMTP mailbox is rejected with a 535 error, the credentials themselves are worth re-checking before anything else.
Availability of Google Workspace mailboxes
The 300 SMTP mailbox trial includes only SMTP mailboxes, and new Google Workspace allotment isn't currently available to purchase — current status: Google Workspace mailboxes.
A note on DKIM and SPF warnings
After connecting, some sequencers display a warning that DKIM, SPF, or DMARC is "not configured". Authentication for your Maildoso domain is set up and managed for you, and these warnings can generally be ignored — they reflect what the checker can see, not what is actually published.
If a mailbox still won't connect after following the steps above, contact us and we'll review your specific case. For a step-by-step Instantly walkthrough, see Connecting your mailboxes to Instantly, and for other connection errors across sequencers, see Troubleshooting sequencer connection errors.