Email server settings
SendGrid SMTP settings
The SendGrid SMTP settings are smtp.sendgrid.net, port 587 with TLS (or 465 with SSL), the user name apikey (that exact word) and an API key as the password. Your SendGrid account login doesn’t work for SMTP.
Last checked October 10, 2026, against Twilio SendGrid’s own documentation.
SendGrid SMTP server and ports
| Server, port and securityServer | Port and security |
|---|---|
| SMTP · outgoingsmtp | 587STARTTLS |
| SMTP · outgoingsmtp | 465SSL/TLS |
| SMTP · outgoingsmtp | 25, 2525STARTTLS |
Sign-in: apikey + API key
User name: the literal word apikey for every account. The password is an API key with at least “Mail” permissions.
SendGrid SMTP settings explained
From Twilio SendGrid’s Integrating with the SMTP API:
- Host:
smtp.sendgrid.net. Don’t hardcode SendGrid’s IP addresses; they “occasionally change without notice”. - Ports: 25, 2525 or 587 for unencrypted or TLS connections, 465 for SSL. SendGrid’s SMTP quick start uses port 587, which “should avoid rate limiting or connection blocking from ISPs and hosting providers”.
- Login: user name
apikey(“the exact string ‘apikey’ and not the API key itself”), with your API key as the password.
SendGrid also requires a verified sender identity: either verify a single sender address (SendGrid emails a confirmation link to it) or authenticate your domain, after which senders on that domain don’t need single sender verification (sender verification). Background on the DNS records behind domain authentication: DKIM record and SPF record.
API key as SMTP password
SMTP logins use an API key, not your account password. SendGrid’s SMTP guide asks for a key “with at least ‘Mail’ permissions”. To create one (API keys):
- In the SendGrid console, go to Settings → API Keys and click Create API Key.
- Enter a name and choose Full Access, or Custom Access with the mail permission only.
- Click Create & View and copy the key. The console shows it only once.
Use a separate key per app, so you can delete one without breaking the others.
Use SendGrid SMTP in an app or test it by hand
In any app or plugin with SMTP fields: host smtp.sendgrid.net, port 587, encryption TLS (STARTTLS), authentication on, user name apikey, with your API key as the password.
To test a key by hand, SendGrid’s SMTP quick start uses Telnet on port 587 and AUTH LOGIN. Both values are Base64-encoded: apikey becomes YXBpa2V5, and the key itself is encoded with echo -n '<YOUR_API_KEY>' | openssl base64. Make sure no line feed or space ends up in the encoded key.
telnet smtp.sendgrid.net 587
AUTH LOGIN
334 VXNlcm5hbWU6
YXBpa2V5
334 UGFzc3dvcmQ6
<your API key, Base64-encoded>
235 Authentication successful
235 Authentication successful confirms that port 587 is open and the key works.
Common SendGrid SMTP errors
| Error or symptom | Fix |
|---|---|
550 Unauthenticated senders not allowed | The app sent mail before logging in. Turn on SMTP authentication with apikey and your API key. |
403 You are not authorized to send from that email address | The From address doesn’t match a verified sender identity. Verify the sender or authenticate its domain. |
451 Authentication failed: Maximum credits exceeded | A daily credit limit is in force on your account. SendGrid asks you to contact support to remove it. |
550 You are temporarily blocked from sending emails due to repeated bad requests | Too many bad sender or recipient addresses in a short time triggered a block of a few minutes. Clean the recipient list before you resend. |
550 Requested action not taken: mailbox unavailable, 551 User does not exist, 553 Invalid/inactive user | Bounces from the recipient’s server: the mailbox doesn’t exist, is malformed or is blocked by policy. Remove the address from your list. |
Error texts from SendGrid’s SMTP errors and troubleshooting page. The codes from receiving servers are explained in the SMTP error codes reference.
SendGrid SMTP limits
SendGrid’s SMTP guide allows up to 5,000 messages per SMTP connection and up to 10,000 concurrent connections from a single server.
Invalid addresses cost twice: each one becomes a hard bounce, and many in a row can trigger the temporary block above. Check addresses at sign-up with an email validation API, or clean an existing list with the bulk email verifier.
Sources
Checked on October 10, 2026. Server names, ports and sign-in rules come from these official pages:
Other SMTP relay services
SendGrid SMTP settings: FAQ
What are the SendGrid SMTP settings?
smtp.sendgrid.net, port 587 with TLS (or 465 with SSL; 25 and 2525 also work), user name apikey, and a SendGrid API key with at least “Mail” permissions as the password.What is the SendGrid SMTP username?
apikey, not your account user name or email address. The API key goes in the password field.Which port should I use for SendGrid SMTP?
Why does SendGrid say “Unauthenticated senders not allowed”?
smtp.sendgrid.net without logging in. Turn on SMTP authentication with apikey and your API key.Email validation API
Validate recipients before you send through SendGrid
emailvalidation.io checks syntax, MX records and the mailbox over SMTP, flags disposable, role and free addresses and returns a quality score, in one request.
/v1/info Email validation API Read the documentation
100 free validations every month. No credit card required.
GET https://api.emailvalidation.io/v1/info?
{
"email": "support@emailvalidation.io",
"user": "support",
"tag": "",
"domain": "emailvalidation.io",
"format_valid": true,
"mx_found": true,
"smtp_check": true,
"catch_all": null,
"role": true,
"disposable": false,
"free": false,
"score": 0.64,
"state": "deliverable",
"reason": "valid_mailbox",
"did_you_mean": ""
}