Warmup Inbox does allow SendGrid. Before connecting you need to
Sign up for a SendGrid account
Create and store a SendGrid API key with full access "Mail Send" permissions.
Verify your Sender Identity
Once complete, here are the SMTP settings you should do.
Email Provider: Other
SMTP Settings:
SMTP Username: apikey
SMTP Password: {{your SendGrid api key}}
SMTP Host: smtp.sendgrid.net
SMTP Port: 465
TLS: TRUE/YES
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SMTP ONLY Option
Under our SMTP only plan, you can directly connect an SMTP only inbox to the platform without the need for IMAP credentials under our Add Inbox page. Please write into support for additional details