Set MX priority 100 or customize to any value
Possbility to add MX record with priority 100 but plesk allows only to select priorities from 0 to 50. For example to enable mail server to work properly at the OVH they require the configuration to priority 100
The actual value of an MX priority does not influence the behavior of other servers directly. It is more a "sorting" criteria. When OVH asks for "100" in a list of their five MX servers as 1, 5, 50, 100, 200, you can also rearrange that list to values like 1, 5, 10, 15, 20 with 15 representing the 100, because it is in the same order "slot" as their manual suggests. Currently you can configure ten MX entries for the same domain, but in real-world configurations we've never encountered a domain where ten MX entries were needed.
If you know of an example where a provider asks for a fixed value like "100" and does not deliver mail if that value is not present in an MX record, please let us know in your comments.
-- PD