Zoho Mail is mainly intended for normal business usage and not for sending our mass emails or marketing emails or newsletters. Any mass email activity may lead to to the detection of unusual activity in your account.
In case there is any unusual email activity automatically detected in your account, we take certain actions to avoid your account being compromised/ misused, control Spam and prevent abuse of Zoho Email by spammers. When there is such a detection, the email outgoing from your account or email incoming to your account, may be temporarily restricted. It might take anywhere from 1 business day to 5 business days for your account to be able to send or receive email depending on the activity detected by our systems. You will still be able to access your account and the data in the account. Unusual email activity includes the following, but is not limited to the below items:
These may lead to your accounts outgoing getting blocked and you will not be able to send emails from webmail or from email clients. You need to contact the Organization Administrator or Zoho Mail support to get your account unblocked.
In case you are sending marketing emails or newsletter, we suggest you to try out Zoho Campaigns, a more apropriate tool that provides you more visibility regarding the reach of your emails and also avoides your account getting blocked due to the limits.
Similarly if there is an unusual activity in your account via IMAP, your IMAP access may be blocked temporarily based on the type of activity detected. The unusual IMAP activity includes the following, but is not limited to the following items:
Some mail clients will automatically open multiple connections in the background and hence you may reach the threshold limit even when you are accessing mail in two or three mail clients.
To avoid simultaneous connection requests, we suggest you to close or sign out of the mail client that you are not actively using. You can also optimize your IMAP connections, by choosing selective folders to sync via IMAP. The option is available in the Folders section of the Settings page. This might optimize your IMAP Access, providing you active connection option and at the same time restricting the number of connections made by the folders.