A record-triggered flow should update a custom field called (number_of_email_sent_c) on the lead object whenever an email is sent to a lead.
how to use the formula to increase the number so the custom field will increment by 1 whenever the flow gets triggered? I'm stuck with this flow, Please help me how to approach this.
#flow
Andrew Russo (BACA Systems) 
Forum Ambassador
in flow add these start conditions
RelatedToId starts with 00Q
Incoming equals False
then do a get records to get the lead that has an id that matches the record that started the flows relatedtoid
ID Equals {!$Record.RelatedToId}
then so an assigment element to add 1 to the record you just located
{!GetLead.customnumberfield__c} ADD 1
then do an update records and say update a record variable then select the record you found in the get records.
