I believe the following should meet your needs:
Code:
Sub Timed_Email_Merge()
' Merges one record at a time to email with a pre-defined delay between messages.
' Sourced from: https://www.msofficeforums.com/mail-merge/38282-email-merge-delay.html
Application.ScreenUpdating = False
Dim i As Long
With ActiveDocument.MailMerge
.Destination = wdSendToEmail
.MailAddressFieldName = "Email"
.MailSubject = "Subject"
.SuppressBlankLines = True
For i = 1 To .DataSource.RecordCount
With .DataSource
.FirstRecord = i
.LastRecord = i
.ActiveRecord = i
End With
.Execute Pause:=False
Call Pause(10)
Next i
End With
Application.ScreenUpdating = True
End Sub
Public Function Pause(Delay As Long)
Dim Start As Long
Start = Timer
If Start + Delay > 86399 Then
Start = 0: Delay = (Start + Delay) Mod 86400
Do While Timer > 1
DoEvents ' Yield to other processes.
Loop
End If
Do While Timer < Start + Delay
DoEvents ' Yield to other processes.
Loop
End Function
Note that you need to edit the lines:
.MailAddressFieldName = "Email"
and:
.MailSubject = "Subject"
to ensure the correct field for the email addresses and the desired email subject line, respectively, are employed.
You can vary the delay by changing the value in:
Call Pause(10)
Presently, it's set for 10 seconds. At that rate, your 300 emails would take 50 minutes to send. With your suggested 90-second intervals, it would take 7.5 hours...
For PC macro installation & usage instructions, see:
Installing Macros