Office 365 and Google Apps both throttle outbound email

Thinking about moving your mail to the cloud? Make sure you understand Microsoft’s and Google’s limitations on the number of emails you can send every day

In a complicated bit of tomfoolery, both Office 365 and Google Apps limit the number of email messages you can send in a day. If you’re thinking about moving to either Office 365 or Google Apps, you should understand how your mail can be blocked in the cloud — and think about paying more for a service that doesn’t block so readily.

There’s been some gnashing of teeth in the Office 365 community about Microsoft Exchange’s forced account shut-down, but many people don’t realize that Google Apps packs similar limitations.

Here’s how it works. Both Office 365 and Google Apps keep track of each individual email account and count how many messages go out from each account.

Office 365 customers that pay for the less-expensive “Small Business and Professionals” or “P” plan are limited to sending 500 emails every 24 hours. They’re also limited to sending 30 messages per minute from each account.

Office 365 customers that shell out for the “Enterprise” or “E” plans get throttled at 1,500 emails every 24 hours. While the official description of the recipient limits defy parsing, it appears as if “E” customers are also limited to 30 emails per minute for each account. (Take a look at Microsoft’s Exchange Server Message and Recipient Limits and see if you can make heads from tails out of it.)

The details are a bit strange. If you send a message to, say, five addresses (either “To” or “CC” or “BCC”), that counts as five sent messages. Easy. If you send a message to a distribution group on the server’s GAL (Global Address List/shared address book), that counts as one outbound message, no matter how many addresses are in the GAL. But if you send a message to a distribution list in your Contacts folder, each individual address gets counted.

For example, say you pay for an Office 365 “P” account, and have a Contacts distribution list consisting of 50 people in your department. Every time you put that distribution list in the To: or CC: or BCC: field of a message, you bump up your 24-hour count by 50 messages. It’s easy to envision a situation where you would hit the 500 message limit. Once a particular email address hits the limit, it’s prevented from sending further messages until the 24-hour running total falls below 500.

If you have an “E” account, the same rules apply, but your 24-hour running total can’t go above 1,500 messages.

Microsoft says “These limits are applied to messages, senders, or recipients to combat spam”. As far as I can tell, it only makes spamming a little more time-consuming and/or expensive — and there’s a very real possibility that a regular Office 365 “P” customer could hit the limit and not have a clue why their mail has been blocked.

(Microsoft’s documentation talks about restricting the number of “message recipients” you can have in a 24-hour period. If you read the details, the restriction doesn’t apply to recipients at all. They’re talking about the number of emails that go out.)

Google’s details are completely different, of course. Rules for the free Google Apps state, “Google will temporarily disable your account if you send messages to more than 500 recipients or if you send a large number of undeliverable messages.” It isn’t clear if the messages to 500 recipients have to go out in the course of a minute, an hour, a day, or a week, although Google assures that if you run afoul of the rule, your account will be reinstated within 24 hours. Google also says that if you use a POP or IMAP client (such as Outlook or Apple Mail) to send your mail, you’re limited to 100 recipients for each message.

If you pay for Google Apps, different rules apply. You can send up to 10,000 messages per day (count the number of entries in the To:, CC:, and BCC: fields), but only 3,000 of those can go outside your primary domain. In addition, you’re limited to sending messages to at most 3,000 unique addresses every day, and up to 2,000 of those can be outside your primary domain.

Clearly, dollar for dollar, Google’s more liberal in its outbound email throttling policies. What isn’t clear is why both Microsoft and Google have two different levels of protection: Pay more money and you can send more spam. It also isn’t clear why going over 500 (or 1,500 or 3,000) messages per day makes you a spammer, drawing the automated ire of the throttling algorithms.

Yet another one of those things Microsoft and Google didn’t warn you about, eh?