How many emails can I send without blacklisting my company email?
Per day: 10 000 recipients.
Per hour: There’s no hourly limit, but a limit per minute, which is 30 messages max.
Additional good-to-know: You won’t even get close to the daily limit of Office 365. 10K per day sounds crazy for quality email but, be aware of the limit per minute, especially if you use some automation to send your outbound emails.
After the recipient rate limit is reached, messages can't be sent from the mailbox until the number of recipients that were sent messages in the past 24 hours drops below the limit. For example, a user sends an email message to 5000 recipients at 09:00 AM, then sends another message to 2500 recipients at 10:00 AM, and then sends another message to 2500 recipients at 11:00 AM, hitting the limit of 10,000 messages. The user won't be able to send messages again until 09:00 AM the next day.
What are my storage limits with 365?
Message Size limits
The following limits are applied to every email message.
Message size limit: Message size limits are necessary to prevent large messages from blocking the delivery of other messages and affecting service performance for all users. These limits include attachments and apply organization-wide to all messages (inbound, outbound, and internal). Messages larger than this limit will not be delivered, and the sender will receive a non-delivery report (NDR). While message size limits can be configured up, down, or on a per-user basis, administrators can also create transport rules to limit the maximum size of any individual attachment.
Some email clients may have lower message size limits or may limit the size of an individual file attachment to a value that is less than the Exchange Online message size limit.
Capacity alerts
365 provides three kinds of notifications when a user's mailbox is nearing, or at, capacity:
1. Warning: The user receives an email warning that the mailbox is approaching the maximum size limit. This warning is intended to encourage users to delete unwanted mail.
2. Prohibit Send: The user receives a prohibit-send notification email when the mailbox size limit is reached. The user can't send new messages until enough email is deleted to bring the mailbox below the size limit.
3. Prohibit Send/Receive: Exchange Online rejects any incoming mail when the mailbox size limit is reached and sends a non-delivery report (NDR) to the sender. The sender has the option to try resending the mail later. To receive messages again, the user must delete email until the mailbox is below the size limit.