SMTP Sending Limit and Email Rate Limits for ISPs – Verizon, Comcast, EarthLink, etc
Internet Service Providers have the most solutions at their disposal to prevent customers from sending out too many emails in a too short period of time. They can achieve it by:
- using email send limits: per day, per hour or per number of recipients;
- blocking the SMTP mail server port (25), so you can’t use a 3rd party SMTP agent to send our your emails;
- using whitelists, so only certain customers can send out mass emails (usually by having customers to purchase an upgrade package).
Major Internet Service Providers – SMTP limit and email rate limits
This article contains information about the email send limits (rate limit) of most important Internet Service Providers, as we collected it from our Easy Mail Merge customers, web resources or directly from the support desk of ISPs. Please do NOT take this information for granted, as each ISP can change its outbound email policy without any prior notification.
This article was last updated in November 2007 and it displays the SMTP email send limit (or rate limit) for the following Internet providers: Verizon, Comcast, EarthLink, Cablevision/Optimum, Road Runner, Cox, AT&T Yahoo!, Charter, BellSouth.
- Verizon Email Send & SMTP Limits
The following restrictions apply when sending emails from a verizon.net email account:
Verizon email send limit – no more than 100 recipients per email message AND max 500 emails (recipients) per hour
- Verizon other SMTP limits – max 2mb per message
- Verizon email-outbound policy –
- Verizon SMTP restriction expiry method – the restriction is automatically lifted 24 hours after the email send limit was reached.
- Comcast Email Send & SMTP Limits
Below you can find the Comcast email send or rate limit for Comcast high speed internet customers. Please note that Comcast can also block port 25 for your connection (triggering the error message: “Error #1: Port25.Secure(SSL); no Socket Error: 10053. Error Number 0x800CC0F”), in order to prevent you (or viruses on your computer) from sending emails using your own SMTP agent:
Comcast email send limit – no more than 1000 recipients per day
- Comcast other SMTP limits – max 10mb per message
- Comcast email-outbound policy –
- Comcast SMTP restriction expiry method – the restriction is automatically lifted 24 hours after the email send limit was reached.
- EarthLink Email Send & SMTP Limits (“SMTP Rate Limiting”)
When you reached your EarthLink email send limit, you will receive the following error message from the EarthLink SMTP server: “error 554: www.earthlink.net/go/bulk – Outbound message limit exceeded”. The following restrictions apply when sending emails from an EarthLink internet connection:
EarthLink email send limit – max 1000 recipients per day
- EarthLink other SMTP limits – N/A
- EarthLink email-outbound policy –
- EarthLink SMTP restriction expiry method – A member of EarthLink ‘s Abuse team will investigate the circumstances that led to your SMTP privileges being suspended. If it is deemed that your use was legitimate, then your SMTP privileges will be reactivated within 24 hours.
- Cablevision Email Send & SMTP Limits (Optimum – OOL)
Cablevision / Optimum does NOT allow customers to send emails using an email client program or SMTP mail server, unless the customer subscribed to “Optimum Online Boost” or “Optimum Online for Business”.
Cablevision/Optimum (OOL) email send limit – maximum 50 recipients at one time
- Cablevision other SMTP limits – max 20mb per outgoing message
- Cablevision/Optimum email-outbound policy –
- Cablevision SMTP restriction expiry method – N/A.
- Road Runner Email Send & SMTP Limits
If your account has reached the email send limit, you will receive the following error message: “ERROR:5.7.1:550 Outbound Mail Refused – YOUR_IP_ADDRESS”. The following restrictions apply when sending emails from a Road Runner internet connection:
Road Runner email send limit – max 1,000 recipients per day per IP
- Road Runner other SMTP limits – max 5mb per message
- Road Runner email-outbound policy –
- Road Runner SMTP restriction expiry method – the suspension is automatically lifted after 24 hours
- Cox Email Send & SMTP Limits
Cox did not publish the official email send limit for Cox High Speed Internet subscribers. According to the Cox web site: “Specific email sending limits are not published because they vary from time to time depending on a variety of factors“. We strongly advise you to contact the Cox support department before sending out large amounts of emails.
- Cox other SMTP limits – max 10mb per message
- Cox email-outbound policy –
- AT&T Yahoo! Email Send & SMTP Limits
Please note that, according to the AT&T Yahoo! Membership Agreement, AT&T Yahoo! can assess a charge of $50.00 per day for unintentional violations or $500.00 per day for deliberate violations of their unsolicited email policy. The following restrictions apply when sending emails from an AT&T Yahoo! Internet/email connection:
AT&T Yahoo! email send limit – no more than 100 recipients per email message
- AT&T Yahoo! other SMTP limits – max 20mb per message, max 50 file attachments
- AT&T Yaho0! email-outbound policy –
- AT&T Yahoo! SMTP restriction expiry method – penalty charges may apply
- Charter Email Rate Limits
If you are a Charter Internet access residential customer and you receive the following error message when trying to send emails: “421 Connection Refused – Customer has exceeded the maximum number of messages allowed per hour”, it means your account SMTP access was temporarily blocked. The following restrictions apply when emailing from a Charter connection:
Charter email send limit – maximum 50 recipients / emails per hour
- Charter other SMTP limits – max 10mb per message
- Charter email-outbound policy –
- Charter SMTP restriction expiry method – wait an hour to send additional emails or brake up the recipients number into smaller groups.
- BellSouth Email Send & Rate Limits
BellSouth does not publish a clear email send limit: “Sending mass, unsolicited e-mail by Service users is prohibited. BellSouth Internet Services reserves the right, in BellSouth’s sole discretion, to determine whether such email constitutes unsolicited messages or transmission. Sending large volumes of unsolicited e-mail to a single user, or group of users, commercial or otherwise, by Service users is prohibited.”.
BellSouth email send limit – BellSouth’s sole discretion
- BellSouth other SMTP limits – max 10mb per message
- BellSouth email-outbound policy –
- BellSouth SMTP restriction expiry method – BellSouth Internet Services may immediately terminate any account which it determines, in its sole discretion, is transmitting or is otherwise connected with any ‘spam’ or other unsolicited bulk email. In addition, because damages are often difficult to quantify, if actual damages cannot be reasonably calculated then BellSouth Internet Services may seek liquidated damages of five dollars (US$5.00) for each piece of ‘spam’ or unsolicited bulk email transmitted from or otherwise connected with your account.
Although we planned to publish the email send (rate) limit for non-US ISPs/regions too (like Europe, Canada, etc), we find it very hard to find this information mainly because: many countries do not have clear anti-spam laws; such email rate limits are not disclosed by Internet Service Providers; there are simply no email-send limits for certain ISPs. Still, we strongly advise you to contact your Internet Service Provider and ask about their outbound email policy and email sending / rate limit, before proceeding with a mass email.