How to avoid recipient limit issues when using CodeTwo Email Signatures for Office 365

Problem:

A recipient limit has been set for emails sent by users in your Microsoft 365 (Office 365) organization. When using CodeTwo Email Signatures for Office 365 in server-side mode, this limit is exceeded when sending emails to distribution lists.

Solution:

This is expected behavior in Exchange Online. When a message goes through Exchange Online connectors, each recipient in the distribution list is counted individually. CodeTwo Email Signatures for Office 365 working in server-side mode uses connectors to route messages through the CodeTwo Email Azure Service to add signatures.

There are three ways to solve the recipient limit issue:

• Exclude distribution lists from server-side signature rules in CodeTwo Email Signatures for Office 365
• Use client-side signatures for emails sent to distribution lists
• Increase the recipient limit in Exchange Online

Excluding distribution lists from server-side signature rules in CodeTwo Email Signatures for Office 365

To avoid hitting the recipient limit, you can prevent emails sent to the affected distribution lists from receiving signatures. To do so:

1. Sign in to the signature management app.
2. Select a server-side signature rule and go to the Recipients step.
3. On the bottom list (exceptions), click Add > Email addresses.

Fig. 1. Creating an exception to prevent emails sent to specific email address from receiving signatures.

4. In the window that opens, provide an email address (or multiple email addresses separated by semicolons) of the affected distribution list(s), as shown in Fig. 2., and click OK.

Fig. 2. Entering email addresses of distribution lists.

5. Repeat steps 2-5 for other server-side rules, if necessary.
6. Click Save & Publish to apply your changes.

Learn more about creating exceptions for signature rules

Using client-side signatures for emails sent to distribution lists

When CodeTwo Email Signatures for Office 365 works in client-side (or combo) mode, it makes use of the modern CodeTwo Signatures Web Add-in for Outlook to add signatures as users type their messages in Outlook for Windows, Outlook for Mac and Outlook on the web (OWA). Emails that get a client-side signature are not routed through the CodeTwo Email Azure Service, which means Exchange Online connectors are not used. And, because of that, when you send an email from Outlook to a distribution list, its members will not be counted individually, and so the recipient limit will not be exceeded.

Learn more about signature modes in CodeTwo Email Signatures for Office 365

How to increase the recipient limit in Exchange Online

You can change the recipient limit in the Exchange admin center or by using PowerShell cmdlets. Note that Exchange Online has a limit of 1000 recipients per email, so this solution will only help if this limit has not already been reached.

• Setting the recipient limit in the Exchange admin center
• Setting the recipient limit with PowerShell

Setting the recipient limit in the Exchange admin center

To change the recipient limit, first sign in to the Exchange admin center and go to Recipients > Mailboxes.

• To change the limit for a single mailbox:

1. Click the mailbox you want to edit.
2. In the pane that opens, click Set recipient limit (Fig. 3.).

Fig. 3. Changing the recipient limit for a single mailbox in the Exchange admin center.

3. Enter the maximum number of allowed recipients (from 1 to 1000) in the Maximum recipients field.
4. Click Save to confirm.

• To change the limit for multiple mailboxes:

1. Select mailboxes from the mailboxes list.
2. Click the ellipsis (…) button and select Set recipient limit from the drop-down menu (Fig. 4.).

Fig. 4. Changing the recipient limit for multiple mailboxes in the Exchange admin center.

3. Enter the maximum number of allowed recipients (from 1 to 1000) in the Maximum recipients field.
4. Click Save to confirm.

Setting the recipient limit with PowerShell

First open the PowerShell console on a workstation and connect to Exchange Online by using the following cmdlet:

Connect-ExchangeOnline -UserPrincipalName <Your UPN>

Learn more about how to connect to Exchange via PowerShell

• To change the limit for a single mailbox, use this command:

Set-Mailbox <UserPrincipalName> -RecipientLimits <value>

where <UserPrincipalName> is the mailbox that you want to edit, and <value> is a number between 1 and 1000.

• To change the limit for multiple mailboxes belonging to a specific distribution list, first use the following cmdlet:

$members = (Get-DistributionGroupMember -Identity "<ListName>")

where <ListName> is the name of the distribution list. Next, to set the new recipient limit for all members of this list, use the cmdlet below:

Foreach ($member in $members) {Set-Mailbox -Identity "$member" -RecipientLimits <value>}

where <value> is a number between 1 and 1000.

When you finish working with the remote PowerShell session, close it using the following cmdlet:

Disconnect-ExchangeOnline